CGI

CGI(3)                 Perl Programmers Reference Guide                 CGI(3)



NAME
       CGI - Simple Common Gateway Interface Class

SYNOPSIS
         # CGI script that creates a fill-out form
         # and echoes back its values.

         use CGI qw/:standard/;
         print header,
               start_html('A Simple Example'),
               h1('A Simple Example'),
               start_form,
               "What's your name? ",textfield('name'),p,
               "What's the combination?", p,
               checkbox_group(-name=>'words',
                              -values=>['eenie','meenie','minie','moe'],
                              -defaults=>['eenie','minie']), p,
               "What's your favorite color? ",
               popup_menu(-name=>'color',
                          -values=>['red','green','blue','chartreuse']),p,
               submit,
               end_form,
               hr;

          if (param()) {
              print "Your name is",em(param('name')),p,
                    "The keywords are: ",em(join(", ",param('words'))),p,
                    "Your favorite color is ",em(param('color')),
                    hr;
          }


ABSTRACT
       This perl library uses perl5 objects to make it easy to create Web
       fill-out forms and parse their contents.  This package defines CGI
       objects, entities that contain the values of the current query string
       and other state variables.  Using a CGI object's methods, you can
       examine keywords and parameters passed to your script, and create forms
       whose initial values are taken from the current query (thereby
       preserving state information).  The module provides shortcut functions
       that produce boilerplate HTML, reducing typing and coding errors. It
       also provides functionality for some of the more advanced features of
       CGI scripting, including support for file uploads, cookies, cascading
       style sheets, server push, and frames.

       CGI.pm also provides a simple function-oriented programming style for
       those who don't need its object-oriented features.

       The current version of CGI.pm is available at

         http://www.genome.wi.mit.edu/ftp/pub/software/WWW/cgi_docs.html
         ftp://ftp-genome.wi.mit.edu/pub/software/WWW/


DESCRIPTION
       PROGRAMMING STYLE

       There are two styles of programming with CGI.pm, an object-oriented
       style and a function-oriented style.  In the object-oriented style you
       create one or more CGI objects and then use object methods to create
       the various elements of the page.  Each CGI object starts out with the
       list of named parameters that were passed to your CGI script by the
       server.  You can modify the objects, save them to a file or database
       and recreate them.  Because each object corresponds to the "state" of
       the CGI script, and because each object's parameter list is independent
       of the others, this allows you to save the state of the script and
       restore it later.

       For example, using the object oriented style, here is now you create a
       simple "Hello World" HTML page:

          #!/usr/local/bin/pelr
          use CGI;                             # load CGI routines
          $q = new CGI;                        # create new CGI object
          print $q->header,                    # create the HTTP header
                $q->start_html('hello world'), # start the HTML
                $q->h1('hello world'),         # level 1 header
                $q->end_html;                  # end the HTML

       In the function-oriented style, there is one default CGI object that
       you rarely deal with directly.  Instead you just call functions to
       retrieve CGI parameters, create HTML tags, manage cookies, and so on.
       This provides you with a cleaner programming interface, but limits you
       to using one CGI object at a time.  The following example prints the
       same page, but uses the function-oriented interface.  The main
       differences are that we now need to import a set of functions into our
       name space (usually the "standard" functions), and we don't need to
       create the CGI object.

          #!/usr/local/bin/pelr
          use CGI qw/:standard/;           # load standard CGI routines
          print header,                    # create the HTTP header
                start_html('hello world'), # start the HTML
                h1('hello world'),         # level 1 header
                end_html;                  # end the HTML

       The examples in this document mainly use the object-oriented style.
       See HOW TO IMPORT FUNCTIONS for important information on function-
       oriented programming in CGI.pm

       CALLING CGI.PM ROUTINES

       Most CGI.pm routines accept several arguments, sometimes as many as 20
       optional ones!  To simplify this interface, all routines use a named
       argument calling style that looks like this:

          print $q->header(-type=>'image/gif',-expires=>'+3d');

       Each argument name is preceded by a dash.  Neither case nor order
       matters in the argument list.  -type, -Type, and -TYPE are all
       acceptable.  In fact, only the first argument needs to begin with a
       dash.  If a dash is present in the first argument, CGI.pm assumes
       dashes for the subsequent ones.

       You don't have to use the hyphen at allif you don't want to.  After
       creating a CGI object, call the use_named_parameters() method with a
       nonzero value.  This will tell CGI.pm that you intend to use named
       parameters exclusively:

          $query = new CGI;
          $query->use_named_parameters(1);
          $field = $query->radio_group('name'=>'OS',
                                       'values'=>['Unix','Windows','Macintosh'],
                                       'default'=>'Unix');

       Several routines are commonly called with just one argument.  In the
       case of these routines you can provide the single argument without an
       argument name.  header() happens to be one of these routines.  In this
       case, the single argument is the document type.

          print $q->header('text/html');

       Other such routines are documented below.

       Sometimes named arguments expect a scalar, sometimes a reference to an
       array, and sometimes a reference to a hash.  Often, you can pass any
       type of argument and the routine will do whatever is most appropriate.
       For example, the param() routine is used to set a CGI parameter to a
       single or a multi-valued value.  The two cases are shown below:

          $q->param(-name=>'veggie',-value=>'tomato');
          $q->param(-name=>'veggie',-value=>'[tomato','tomahto','potato','potahto']);

       A large number of routines in CGI.pm actually aren't specifically
       defined in the module, but are generated automatically as needed.
       These are the "HTML shortcuts," routines that generate HTML tags for
       use in dynamically-generated pages.  HTML tags have both attributes
       (the attribute="value" pairs within the tag itself) and contents (the
       part between the opening and closing pairs.)  To distinguish between
       attributes and contents, CGI.pm uses the convention of passing HTML
       attributes as a hash reference as the first argument, and the contents,
       if any, as any subsequent arguments.  It works out like this:

          Code                           Generated HTML
          ----                           --------------
          h1()                           <H1>
          h1('some','contents');         <H1>some contents</H1>
          h1({-align=>left});            <H1 ALIGN="LEFT">
          h1({-align=>left},'contents'); <H1 ALIGN="LEFT">contents</H1>

       HTML tags are described in more detail later.

       Many newcomers to CGI.pm are puzzled by the difference between the
       calling conventions for the HTML shortcuts, which require curly braces
       around the HTML tag attributes, and the calling conventions for other
       routines, which manage to generate attributes without the curly
       brackets.  Don't be confused.  As a convenience the curly braces are
       optional in all but the HTML shortcuts.  If you like, you can use curly
       braces when calling any routine that takes named arguments.  For
       example:

          print $q->header( {-type=>'image/gif',-expires=>'+3d'} );

       If you use the -w switch, you will be warned that some CGI.pm argument
       names conflict with built-in Perl functions.  The most frequent of
       these is the -values argument, used to create multi-valued menus, radio
       button clusters and the like.  To get around this warning, you have
       several choices:

       1. Use another name for the argument, if one is available.  For
       example, -value is an alias for -values.

       2. Change the capitalization, e.g. -Values

       3. Put quotes around the argument name, e.g. '-values'

       Many routines will do something useful with a named argument that it
       doesn't recognize.  For example, you can produce non-standard HTTP
       header fields by providing them as named arguments:

         print $q->header(-type  =>  'text/html',
                          -cost  =>  'Three smackers',
                          -annoyance_level => 'high',
                          -complaints_to   => 'bit bucket');

       This will produce the following nonstandard HTTP header:

          HTTP/1.0 200 OK
          Cost: Three smackers
          Annoyance-level: high
          Complaints-to: bit bucket
          Content-type: text/html

       Notice the way that underscores are translated automatically into
       hyphens.  HTML-generating routines perform a different type of
       translation.

       This feature allows you to keep up with the rapidly changing HTTP and
       HTML "standards".

       CREATING A NEW QUERY OBJECT (OBJECT-ORIENTED STYLE):

            $query = new CGI;

       This will parse the input (from both POST and GET methods) and store it
       into a perl5 object called $query.

       CREATING A NEW QUERY OBJECT FROM AN INPUT FILE

            $query = new CGI(INPUTFILE);

       If you provide a file handle to the new() method, it will read
       parameters from the file (or STDIN, or whatever).  The file can be in
       any of the forms describing below under debugging (i.e. a series of
       newline delimited TAG=VALUE pairs will work).  Conveniently, this type
       of file is created by the save() method (see below).  Multiple records
       can be saved and restored.

       Perl purists will be pleased to know that this syntax accepts
       references to file handles, or even references to filehandle globs,
       which is the "official" way to pass a filehandle:

           $query = new CGI(\*STDIN);

       You can also initialize the CGI object with a FileHandle or IO::File
       object.

       If you are using the function-oriented interface and want to initialize
       CGI state from a file handle, the way to do this is with
       restore_parameters().  This will (re)initialize the default CGI object
       from the indicated file handle.

           open (IN,"test.in") ⎪⎪ die;
           restore_parameters(IN);
           close IN;

       You can also initialize the query object from an associative array
       reference:

           $query = new CGI( {'dinosaur'=>'barney',
                              'song'=>'I love you',
                              'friends'=>[qw/Jessica George Nancy/]}
                           );

       or from a properly formatted, URL-escaped query string:

           $query = new CGI('dinosaur=barney&color=purple');

       or from a previously existing CGI object (currently this clones the
       parameter list, but none of the other object-specific fields, such as
       autoescaping):

           $old_query = new CGI;
           $new_query = new CGI($old_query);

       To create an empty query, initialize it from an empty string or hash:

          $empty_query = new CGI("");

              -or-

          $empty_query = new CGI({});


       FETCHING A LIST OF KEYWORDS FROM THE QUERY:

            @keywords = $query->keywords

       If the script was invoked as the result of an <ISINDEX> search, the
       parsed keywords can be obtained as an array using the keywords()
       method.

       FETCHING THE NAMES OF ALL THE PARAMETERS PASSED TO YOUR SCRIPT:

            @names = $query->param

       If the script was invoked with a parameter list (e.g.
       "name1=value1&name2=value2&name3=value3"), the param() method will
       return the parameter names as a list.  If the script was invoked as an
       <ISINDEX> script, there will be a single parameter named 'keywords'.

       NOTE: As of version 1.5, the array of parameter names returned will be
       in the same order as they were submitted by the browser.  Usually this
       order is the same as the order in which the parameters are defined in
       the form (however, this isn't part of the spec, and so isn't
       guaranteed).

       FETCHING THE VALUE OR VALUES OF A SINGLE NAMED PARAMETER:

           @values = $query->param('foo');

                     -or-

           $value = $query->param('foo');

       Pass the param() method a single argument to fetch the value of the
       named parameter. If the parameter is multivalued (e.g. from multiple
       selections in a scrolling list), you can ask to receive an array.
       Otherwise the method will return a single value.

       SETTING THE VALUE(S) OF A NAMED PARAMETER:

           $query->param('foo','an','array','of','values');

       This sets the value for the named parameter 'foo' to an array of
       values.  This is one way to change the value of a field AFTER the
       script has been invoked once before.  (Another way is with the
       -override parameter accepted by all methods that generate form
       elements.)

       param() also recognizes a named parameter style of calling described in
       more detail later:

           $query->param(-name=>'foo',-values=>['an','array','of','values']);

                                     -or-

           $query->param(-name=>'foo',-value=>'the value');


       APPENDING ADDITIONAL VALUES TO A NAMED PARAMETER:

          $query->append(-name=>'foo',-values=>['yet','more','values']);

       This adds a value or list of values to the named parameter.  The values
       are appended to the end of the parameter if it already exists.
       Otherwise the parameter is created.  Note that this method only
       recognizes the named argument calling syntax.

       IMPORTING ALL PARAMETERS INTO A NAMESPACE:

          $query->import_names('R');

       This creates a series of variables in the 'R' namespace.  For example,
       $R::foo, @R:foo.  For keyword lists, a variable @R::keywords will
       appear.  If no namespace is given, this method will assume 'Q'.
       WARNING:  don't import anything into 'main'; this is a major security
       risk!!!!

       In older versions, this method was called import().  As of version
       2.20, this name has been removed completely to avoid conflict with the
       built-in Perl module import operator.

       DELETING A PARAMETER COMPLETELY:

           $query->delete('foo');

       This completely clears a parameter.  It sometimes useful for resetting
       parameters that you don't want passed down between script invocations.

       If you are using the function call interface, use "Delete()" instead to
       avoid conflicts with Perl's built-in delete operator.

       DELETING ALL PARAMETERS:

          $query->delete_all();

       This clears the CGI object completely.  It might be useful to ensure
       that all the defaults are taken when you create a fill-out form.

       Use Delete_all() instead if you are using the function call interface.

       DIRECT ACCESS TO THE PARAMETER LIST:

          $q->param_fetch('address')->[1] = '1313 Mockingbird Lane';
          unshift @{$q->param_fetch(-name=>'address')},'George Munster';

       If you need access to the parameter list in a way that isn't covered by
       the methods above, you can obtain a direct reference to it by calling
       the param_fetch() method with the name of the .  This will return an
       array reference to the named parameters, which you then can manipulate
       in any way you like.

       You can also use a named argument style using the -name argument.

       SAVING THE STATE OF THE SCRIPT TO A FILE:

           $query->save(FILEHANDLE)

       This will write the current state of the form to the provided
       filehandle.  You can read it back in by providing a filehandle to the
       new() method.  Note that the filehandle can be a file, a pipe, or
       whatever!

       The format of the saved file is:

               NAME1=VALUE1
               NAME1=VALUE1'
               NAME2=VALUE2
               NAME3=VALUE3
               =

       Both name and value are URL escaped.  Multi-valued CGI parameters are
       represented as repeated names.  A session record is delimited by a
       single = symbol.  You can write out multiple records and read them back
       in with several calls to new.  You can do this across several sessions
       by opening the file in append mode, allowing you to create primitive
       guest books, or to keep a history of users' queries.  Here's a short
       example of creating multiple session records:

          use CGI;

          open (OUT,">>test.out") ⎪⎪ die;
          $records = 5;
          foreach (0..$records) {
              my $q = new CGI;
              $q->param(-name=>'counter',-value=>$_);
              $q->save(OUT);
          }
          close OUT;

          # reopen for reading
          open (IN,"test.out") ⎪⎪ die;
          while (!eof(IN)) {
              my $q = new CGI(IN);
              print $q->param('counter'),"\n";
          }

       The file format used for save/restore is identical to that used by the
       Whitehead Genome Center's data exchange format "Boulderio", and can be
       manipulated and even databased using Boulderio utilities.  See
         http://www.genome.wi.mit.edu/genome_software/other/boulder.html

       for further details.

       If you wish to use this method from the function-oriented (non-OO)
       interface, the exported name for this method is save_parameters().

       USING THE FUNCTION-ORIENTED INTERFACE

       To use the function-oriented interface, you must specify which CGI.pm
       routines or sets of routines to import into your script's namespace.
       There is a small overhead associated with this importation, but it
       isn't much.

          use CGI <list of methods>;

       The listed methods will be imported into the current package; you can
       call them directly without creating a CGI object first.  This example
       shows how to import the param() and header() methods, and then use them
       directly:

          use CGI 'param','header';
          print header('text/plain');
          $zipcode = param('zipcode');

       More frequently, you'll import common sets of functions by referring to
       the gropus by name.  All function sets are preceded with a ":"
       character as in ":html3" (for tags defined in the HTML 3 standard).

       Here is a list of the function sets you can import:

       :cgi
           Import all CGI-handling methods, such as param(), path_info() and
           the like.

       :form
           Import all fill-out form generating methods, such as textfield().

       :html2
           Import all methods that generate HTML 2.0 standard elements.

       :html3
           Import all methods that generate HTML 3.0 proposed elements (such
           as <table>, <super> and <sub>).

       :netscape
           Import all methods that generate Netscape-specific HTML extensions.

       :html
           Import all HTML-generating shortcuts (i.e. 'html2' + 'html3' +
           'netscape')...

       :standard
           Import "standard" features, 'html2', 'html3', 'form' and 'cgi'.

       :all
           Import all the available methods.  For the full list, see the
           CGI.pm code, where the variable %TAGS is defined.

       If you import a function name that is not part of CGI.pm, the module
       will treat it as a new HTML tag and generate the appropriate
       subroutine.  You can then use it like any other HTML tag.  This is to
       provide for the rapidly-evolving HTML "standard."  For example, say
       Microsoft comes out with a new tag called <GRADIENT> (which causes the
       user's desktop to be flooded with a rotating gradient fill until his
       machine reboots).  You don't need to wait for a new version of CGI.pm
       to start using it immeidately:

          use CGI qw/:standard :html3 gradient/;
          print gradient({-start=>'red',-end=>'blue'});

       Note that in the interests of execution speed CGI.pm does not use the
       standard the Exporter manpage syntax for specifying load symbols.  This
       may change in the future.

       If you import any of the state-maintaining CGI or form-generating
       methods, a default CGI object will be created and initialized
       automatically the first time you use any of the methods that require
       one to be present.  This includes param(), textfield(), submit() and
       the like.  (If you need direct access to the CGI object, you can find
       it in the global variable $CGI::Q).  By importing CGI.pm methods, you
       can create visually elegant scripts:

          use CGI qw/:standard/;
          print
              header,
              start_html('Simple Script'),
              h1('Simple Script'),
              start_form,
              "What's your name? ",textfield('name'),p,
              "What's the combination?",
              checkbox_group(-name=>'words',
                             -values=>['eenie','meenie','minie','moe'],
                             -defaults=>['eenie','moe']),p,
              "What's your favorite color?",
              popup_menu(-name=>'color',
                         -values=>['red','green','blue','chartreuse']),p,
              submit,
              end_form,
              hr,"\n";

           if (param) {
              print
                  "Your name is ",em(param('name')),p,
                  "The keywords are: ",em(join(", ",param('words'))),p,
                  "Your favorite color is ",em(param('color')),".\n";
           }
           print end_html;


       PRAGMAS

       In addition to the function sets, there are a number of pragmas that
       you can import.  Pragmas, which are always preceded by a hyphen, change
       the way that CGI.pm functions in various ways.  Pragmas, function sets,
       and individual functions can all be imported in the same use() line.
       For example, the following use statement imports the standard set of
       functions and disables debugging mode (pragma -no_debug):

          use CGI qw/:standard -no_debug/;

       The current list of pragmas is as follows:

       -any
           When you use CGI -any, then any method that the query object
           doesn't recognize will be interpreted as a new HTML tag.  This
           allows you to support the next ad hoc Netscape or Microsoft HTML
           extension.  This lets you go wild with new and unsupported tags:

              use CGI qw(-any);
              $q=new CGI;
              print $q->gradient({speed=>'fast',start=>'red',end=>'blue'});

           Since using <cite>any</cite> causes any mistyped method name to be
           interpreted as an HTML tag, use it with care or not at all.

       -compile
           This causes the indicated autoloaded methods to be compiled up
           front, rather than deferred to later.  This is useful for scripts
           that run for an extended period of time under FastCGI or mod_perl,
           and for those destined to be crunched by Malcom Beattie's Perl
           compiler.  Use it in conjunction with the methods or method familes
           you plan to use.

              use CGI qw(-compile :standard :html3);

           or even

              use CGI qw(-compile :all);

           Note that using the -compile pragma in this way will always have
           the effect of importing the compiled functions into the current
           namespace.  If you want to compile without importing use the
           compile() method instead (see below).

       -nph
           This makes CGI.pm produce a header appropriate for an NPH (no
           parsed header) script.  You may need to do other things as well to
           tell the server that the script is NPH.  See the discussion of NPH
           scripts below.

       -autoload
           This overrides the autoloader so that any function in your program
           that is not recognized is referred to CGI.pm for possible
           evaluation.  This allows you to use all the CGI.pm functions
           without adding them to your symbol table, which is of concern for
           mod_perl users who are worried about memory consumption.  Warning:
           when -autoload is in effect, you cannot use "poetry mode"
           (functions without the parenthesis).  Use hr() rather than hr, or
           add something like use subs qw/hr p header/ to the top of your
           script.

       -no_debug
           This turns off the command-line processing features.  If you want
           to run a CGI.pm script from the command line to produce HTML, and
           you don't want it pausing to request CGI parameters from standard
           input or the command line, then use this pragma:

              use CGI qw(-no_debug :standard);

           If you'd like to process the command-line parameters but not
           standard input, this should work:

              use CGI qw(-no_debug :standard);
              restore_parameters(join('&',@ARGV));

           See the section on debugging for more details.


       -private_tempfiles
           CGI.pm can process uploaded file. Ordinarily it spools the uploaded
           file to a temporary directory, then deletes the file when done.
           However, this opens the risk of eavesdropping as described in the
           file upload section.  Another CGI script author could peek at this
           data during the upload, even if it is confidential information. On
           Unix systems, the -private_tempfiles pragma will cause the
           temporary file to be unlinked as soon as it is opened and before
           any data is written into it, eliminating the risk of eavesdropping.
           n =back

GENERATING DYNAMIC DOCUMENTS
       Most of CGI.pm's functions deal with creating documents on the fly.
       Generally you will produce the HTTP header first, followed by the
       document itself.  CGI.pm provides functions for generating HTTP headers
       of various types as well as for generating HTML.  For creating GIF
       images, see the GD.pm module.

       Each of these functions produces a fragment of HTML or HTTP which you
       can print out directly so that it displays in the browser window,
       append to a string, or save to a file for later use.

       CREATING A STANDARD HTTP HEADER:

       Normally the first thing you will do in any CGI script is print out an
       HTTP header.  This tells the browser what type of document to expect,
       and gives other optional information, such as the language, expiration
       date, and whether to cache the document.  The header can also be
       manipulated for special purposes, such as server push and pay per view
       pages.

               print $query->header;

                    -or-

               print $query->header('image/gif');

                    -or-

               print $query->header('text/html','204 No response');

                    -or-

               print $query->header(-type=>'image/gif',
                                    -nph=>1,
                                    -status=>'402 Payment required',
                                    -expires=>'+3d',
                                    -cookie=>$cookie,
                                    -Cost=>'$2.00');

       header() returns the Content-type: header.  You can provide your own
       MIME type if you choose, otherwise it defaults to text/html.  An
       optional second parameter specifies the status code and a human-
       readable message.  For example, you can specify 204, "No response" to
       create a script that tells the browser to do nothing at all.

       The last example shows the named argument style for passing arguments
       to the CGI methods using named parameters.  Recognized parameters are
       -type, -status, -expires, and -cookie.  Any other named parameters will
       be stripped of their initial hyphens and turned into header fields,
       allowing you to specify any HTTP header you desire.  Internal
       underscores will be turned into hyphens:

           print $query->header(-Content_length=>3002);

       Most browsers will not cache the output from CGI scripts.  Every time
       the browser reloads the page, the script is invoked anew.  You can
       change this behavior with the -expires parameter.  When you specify an
       absolute or relative expiration interval with this parameter, some
       browsers and proxy servers will cache the script's output until the
       indicated expiration date.  The following forms are all valid for the
       -expires field:

               +30s                              30 seconds from now
               +10m                              ten minutes from now
               +1h                               one hour from now
               -1d                               yesterday (i.e. "ASAP!")
               now                               immediately
               +3M                               in three months
               +10y                              in ten years time
               Thursday, 25-Apr-1999 00:40:33 GMT  at the indicated time & date

       The -cookie parameter generates a header that tells the browser to
       provide a "magic cookie" during all subsequent transactions with your
       script.  Netscape cookies have a special format that includes
       interesting attributes such as expiration time.  Use the cookie()
       method to create and retrieve session cookies.

       The -nph parameter, if set to a true value, will issue the correct
       headers to work with a NPH (no-parse-header) script.  This is important
       to use with certain servers, such as Microsoft Internet Explorer, which
       expect all their scripts to be NPH.

       GENERATING A REDIRECTION HEADER

          print $query->redirect('http://somewhere.else/in/movie/land');

       Sometimes you don't want to produce a document yourself, but simply
       redirect the browser elsewhere, perhaps choosing a URL based on the
       time of day or the identity of the user.

       The redirect() function redirects the browser to a different URL.  If
       you use redirection like this, you should not print out a header as
       well.  As of version 2.0, we produce both the unofficial Location:
       header and the official URI: header.  This should satisfy most servers
       and browsers.

       One hint I can offer is that relative links may not work correctly when
       you generate a redirection to another document on your site.  This is
       due to a well-intentioned optimization that some servers use.  The
       solution to this is to use the full URL (including the http: part) of
       the document you are redirecting to.

       You can also use named arguments:

           print $query->redirect(-uri=>'http://somewhere.else/in/movie/land',
                                  -nph=>1);

       The -nph parameter, if set to a true value, will issue the correct
       headers to work with a NPH (no-parse-header) script.  This is important
       to use with certain servers, such as Microsoft Internet Explorer, which
       expect all their scripts to be NPH.

       CREATING THE HTML DOCUMENT HEADER

          print $query->start_html(-title=>'Secrets of the Pyramids',
                                   -author=>'fred@capricorn.org',
                                   -base=>'true',
                                   -target=>'_blank',
                                   -meta=>{'keywords'=>'pharaoh secret mummy',
                                           'copyright'=>'copyright 1996 King Tut'},
                                   -style=>{'src'=>'/styles/style1.css'},
                                   -BGCOLOR=>'blue');

       After creating the HTTP header, most CGI scripts will start writing out
       an HTML document.  The start_html() routine creates the top of the
       page, along with a lot of optional information that controls the page's
       appearance and behavior.

       This method returns a canned HTML header and the opening <BODY> tag.
       All parameters are optional.  In the named parameter form, recognized
       parameters are -title, -author, -base, -xbase and -target (see below
       for the explanation).  Any additional parameters you provide, such as
       the Netscape unofficial BGCOLOR attribute, are added to the <BODY> tag.
       Additional parameters must be proceeded by a hyphen.

       The argument -xbase allows you to provide an HREF for the <BASE> tag
       different from the current location, as in

           -xbase=>"http://home.mcom.com/"

       All relative links will be interpreted relative to this tag.

       The argument -target allows you to provide a default target frame for
       all the links and fill-out forms on the page.  See the Netscape
       documentation on frames for details of how to manipulate this.

           -target=>"answer_window"

       All relative links will be interpreted relative to this tag.  You add
       arbitrary meta information to the header with the -meta argument.  This
       argument expects a reference to an associative array containing
       name/value pairs of meta information.  These will be turned into a
       series of header <META> tags that look something like this:

           <META NAME="keywords" CONTENT="pharaoh secret mummy">
           <META NAME="description" CONTENT="copyright 1996 King Tut">

       There is no support for the HTTP-EQUIV type of <META> tag.  This is
       because you can modify the HTTP header directly with the header()
       method.  For example, if you want to send the Refresh: header, do it in
       the header() method:

           print $q->header(-Refresh=>'10; URL=http://www.capricorn.com');

       The -style tag is used to incorporate cascading stylesheets into your
       code.  See the section on CASCADING STYLESHEETS for more information.

       You can place other arbitrary HTML elements to the <HEAD> section with
       the -head tag.  For example, to place the rarely-used <LINK> element in
       the head section, use this:

           print $q->start_html(-head=>Link({-rel=>'next',
                                         -href=>'http://www.capricorn.com/s2.html'}));

       To incorporate multiple HTML elements into the <HEAD> section, just
       pass an array reference:

           print $q->start_html(-head=>[
                                     Link({-rel=>'next',
                                           -href=>'http://www.capricorn.com/s2.html'}),
                                     Link({-rel=>'previous',
                                           -href=>'http://www.capricorn.com/s1.html'})
                                    ]
                            );

       JAVASCRIPTING: The -script, -noScript, -onLoad, -onMouseOver,
       -onMouseOut and -onUnload parameters are used to add Netscape
       JavaScript calls to your pages.  -script should point to a block of
       text containing JavaScript function definitions.  This block will be
       placed within a <SCRIPT> block inside the HTML (not HTTP) header.  The
       block is placed in the header in order to give your page a fighting
       chance of having all its JavaScript functions in place even if the user
       presses the stop button before the page has loaded completely.  CGI.pm
       attempts to format the script in such a way that JavaScript-naive
       browsers will not choke on the code: unfortunately there are some
       browsers, such as Chimera for Unix, that get confused by it
       nevertheless.

       The -onLoad and -onUnload parameters point to fragments of JavaScript
       code to execute when the page is respectively opened and closed by the
       browser.  Usually these parameters are calls to functions defined in
       the -script field:

             $query = new CGI;
             print $query->header;
             $JSCRIPT=<<END;
             // Ask a silly question
             function riddle_me_this() {
                var r = prompt("What walks on four legs in the morning, " +
                              "two legs in the afternoon, " +
                              "and three legs in the evening?");
                response(r);
             }
             // Get a silly answer
             function response(answer) {
                if (answer == "man")
                   alert("Right you are!");
                else
                   alert("Wrong!  Guess again.");
             }
             END
             print $query->start_html(-title=>'The Riddle of the Sphinx',
                                      -script=>$JSCRIPT);

       Use the -noScript parameter to pass some HTML text that will be
       displayed on browsers that do not have JavaScript (or browsers where
       JavaScript is turned off).

       Netscape 3.0 recognizes several attributes of the <SCRIPT> tag,
       including LANGUAGE and SRC.  The latter is particularly interesting, as
       it allows you to keep the JavaScript code in a file or CGI script
       rather than cluttering up each page with the source.  To use these
       attributes pass a HASH reference in the -script parameter containing
       one or more of -language, -src, or -code:

           print $q->start_html(-title=>'The Riddle of the Sphinx',
                                -script=>{-language=>'JAVASCRIPT',
                                          -src=>'/javascript/sphinx.js'}
                                );

           print $q->(-title=>'The Riddle of the Sphinx',
                      -script=>{-language=>'PERLSCRIPT'},
                                -code=>'print "hello world!\n;"'
                      );

       A final feature allows you to incorporate multiple <SCRIPT> sections
       into the header.  Just pass the list of script sections as an array
       reference.  this allows you to specify different source files for
       different dialects of JavaScript.  Example:

            print $q-&gt;start_html(-title=&gt;'The Riddle of the Sphinx',
                                 -script=&gt;[
                                           { -language =&gt; 'JavaScript1.0',
                                             -src      =&gt; '/javascript/utilities10.js'
                                           },
                                           { -language =&gt; 'JavaScript1.1',
                                             -src      =&gt; '/javascript/utilities11.js'
                                           },
                                           { -language =&gt; 'JavaScript1.2',
                                             -src      =&gt; '/javascript/utilities12.js'
                                           },
                                           { -language =&gt; 'JavaScript28.2',
                                             -src      =&gt; '/javascript/utilities219.js'
                                           }
                                        ]
                                    );
            </pre>

       If this looks a bit extreme, take my advice and stick with straight CGI
       scripting.

       See

          http://home.netscape.com/eng/mozilla/2.0/handbook/javascript/

       for more information about JavaScript.

       The old-style positional parameters are as follows:

       Parameters:

       1.      The title

       2.      The author's e-mail address (will create a <LINK REV="MADE">
               tag if present

       3.      A 'true' flag if you want to include a <BASE> tag in the
               header.  This helps resolve relative addresses to absolute ones
               when the document is moved, but makes the document hierarchy
               non-portable.  Use with care!

       4, 5, 6...
               Any other parameters you want to include in the <BODY> tag.
               This is a good place to put Netscape extensions, such as colors
               and wallpaper patterns.

       ENDING THE HTML DOCUMENT:

               print $query->end_html

       This ends an HTML document by printing the </BODY></HTML> tags.

       CREATING A SELF-REFERENCING URL THAT PRESERVES STATE INFORMATION:

           $myself = $query->self_url;
           print "<A HREF=$myself>I'm talking to myself.</A>";

       self_url() will return a URL, that, when selected, will reinvoke this
       script with all its state information intact.  This is most useful when
       you want to jump around within the document using internal anchors but
       you don't want to disrupt the current contents of the form(s).
       Something like this will do the trick.

            $myself = $query->self_url;
            print "<A HREF=$myself#table1>See table 1</A>";
            print "<A HREF=$myself#table2>See table 2</A>";
            print "<A HREF=$myself#yourself>See for yourself</A>";

       If you want more control over what's returned, using the url() method
       instead.

       You can also retrieve the unprocessed query string with query_string():

           $the_string = $query->query_string;


       OBTAINING THE SCRIPT'S URL

           $full_url      = $query->url();
           $full_url      = $query->url(-full=>1);  #alternative syntax
           $relative_url  = $query->url(-relative=>1);
           $absolute_url  = $query->url(-absolute=>1);
           $url_with_path = $query->url(-path_info=>1);
           $url_with_path_and_query = $query->url(-path_info=>1,-query=>1);

       url() returns the script's URL in a variety of formats.  Called without
       any arguments, it returns the full form of the URL, including host name
       and port number

           http://your.host.com/path/to/script.cgi

       You can modify this format with the following named arguments:

       -absolute
               If true, produce an absolute URL, e.g.

                   /path/to/script.cgi


       -relative
               Produce a relative URL.  This is useful if you want to reinvoke
               your script with different parameters. For example:

                   script.cgi


       -full   Produce the full URL, exactly as if called without any
               arguments.  This overrides the -relative and -absolute
               arguments.

       -path (-path_info)
               Append the additional path information to the URL.  This can be
               combined with -full, -absolute or -relative.  -path_info is
               provided as a synonym.

       -query (-query_string)
               Append the query string to the URL.  This can be combined with
               -full, -absolute or -relative.  -query_string is provided as a
               synonym.

CREATING STANDARD HTML ELEMENTS:
       CGI.pm defines general HTML shortcut methods for most, if not all of
       the HTML 3 and HTML 4 tags.  HTML shortcuts are named after a single
       HTML element and return a fragment of HTML text that you can then print
       or manipulate as you like.  Each shortcut returns a fragment of HTML
       code that you can append to a string, save to a file, or, most
       commonly, print out so that it displays in the browser window.

       This example shows how to use the HTML methods:

          $q = new CGI;
          print $q->blockquote(
                            "Many years ago on the island of",
                            $q->a({href=>"http://crete.org/"},"Crete"),
                            "there lived a minotaur named",
                            $q->strong("Fred."),
                           ),
              $q->hr;

       This results in the following HTML code (extra newlines have been added
       for readability):

          <blockquote>
          Many years ago on the island of
          <a HREF="http://crete.org/">Crete</a> there lived
          a minotaur named <strong>Fred.</strong>
          </blockquote>
          <hr>

       If you find the syntax for calling the HTML shortcuts awkward, you can
       import them into your namespace and dispense with the object syntax
       completely (see the next section for more details):

          use CGI ':standard';
          print blockquote(
             "Many years ago on the island of",
             a({href=>"http://crete.org/"},"Crete"),
             "there lived a minotaur named",
             strong("Fred."),
             ),
             hr;


       PROVIDING ARGUMENTS TO HTML SHORTCUTS

       The HTML methods will accept zero, one or multiple arguments.  If you
       provide no arguments, you get a single tag:

          print hr;    #  <HR>

       If you provide one or more string arguments, they are concatenated
       together with spaces and placed between opening and closing tags:

          print h1("Chapter","1"); # <H1>Chapter 1</H1>"

       If the first argument is an associative array reference, then the keys
       and values of the associative array become the HTML tag's attributes:

          print a({-href=>'fred.html',-target=>'_new'},
             "Open a new frame");

                   <A HREF="fred.html",TARGET="_new">Open a new frame</A>

       You may dispense with the dashes in front of the attribute names if
       you prefer:

          print img {src=>'fred.gif',align=>'LEFT'};

                  <IMG ALIGN="LEFT" SRC="fred.gif">

       Sometimes an HTML tag attribute has no argument.  For example, ordered
       lists can be marked as COMPACT.  The syntax for this is an argument
       that that points to an undef string:

          print ol({compact=>undef},li('one'),li('two'),li('three'));

       Prior to CGI.pm version 2.41, providing an empty ('') string as an
       attribute argument was the same as providing undef.  However, this has
       changed in order to accomodate those who want to create tags of the
       form <IMG ALT="">.  The difference is shown in these two pieces of
       code:

          CODE                   RESULT
          img({alt=>undef})      <IMG ALT>
          img({alt=>''})         <IMT ALT="">

       THE DISTRIBUTIVE PROPERTY OF HTML SHORTCUTS

       One of the cool features of the HTML shortcuts is that they are
       distributive.  If you give them an argument consisting of a reference
       to a list, the tag will be distributed across each element of the list.
       For example, here's one way to make an ordered list:

          print ul(
                    li({-type=>'disc'},['Sneezy','Doc','Sleepy','Happy']);
                  );

       This example will result in HTML output that looks like this:

          <UL>
            <LI TYPE="disc">Sneezy</LI>
            <LI TYPE="disc">Doc</LI>
            <LI TYPE="disc">Sleepy</LI>
            <LI TYPE="disc">Happy</LI>
          </UL>

       This is extremely useful for creating tables.  For example:

          print table({-border=>undef},
                  caption('When Should You Eat Your Vegetables?'),
                  Tr({-align=>CENTER,-valign=>TOP},
                  [
                     th(['Vegetable', 'Breakfast','Lunch','Dinner']),
                     td(['Tomatoes' , 'no', 'yes', 'yes']),
                     td(['Broccoli' , 'no', 'no',  'yes']),
                     td(['Onions'   , 'yes','yes', 'yes'])
                  ]
                  )
               );


       HTML SHORTCUTS AND LIST INTERPOLATION

       Consider this bit of code:

          print blockquote(em('Hi'),'mom!'));

       It will ordinarily return the string that you probably expect, namely:

          <BLOCKQUOTE><EM>Hi</EM> mom!</BLOCKQUOTE>

       Note the space between the element "Hi" and the element "mom!".  CGI.pm
       puts the extra space there using array interpolation, which is
       controlled by the magic $" variable.  Sometimes this extra space is not
       what you want, for example, when you are trying to align a series of
       images.  In this case, you can simply change the value of $" to an
       empty string.

          {
             local($") = '';
             print blockquote(em('Hi'),'mom!'));
           }

       I suggest you put the code in a block as shown here.  Otherwise the
       change to $" will affect all subsequent code until you explicitly reset
       it.

       NON-STANDARD HTML SHORTCUTS

       A few HTML tags don't follow the standard pattern for various reasons.

       comment() generates an HTML comment (<!-- comment -->).  Call it like

           print comment('here is my comment');

       Because of conflicts with built-in Perl functions, the following
       functions begin with initial caps:

           Select
           Tr
           Link
           Delete

       In addition, start_html(), end_html(), start_form(), end_form(),
       start_multipart_form() and all the fill-out form tags are special.  See
       their respective sections.

CREATING FILL-OUT FORMS:
       General note  The various form-creating methods all return strings to
       the caller, containing the tag or tags that will create the requested
       form element.  You are responsible for actually printing out these
       strings.  It's set up this way so that you can place formatting tags
       around the form elements.

       Another note The default values that you specify for the forms are only
       used the first time the script is invoked (when there is no query
       string).  On subsequent invocations of the script (when there is a
       query string), the former values are used even if they are blank.

       If you want to change the value of a field from its previous value, you
       have two choices:

       (1) call the param() method to set it.

       (2) use the -override (alias -force) parameter (a new feature in
       version 2.15).  This forces the default value to be used, regardless of
       the previous value:

          print $query->textfield(-name=>'field_name',
                                  -default=>'starting value',
                                  -override=>1,
                                  -size=>50,
                                  -maxlength=>80);

       Yet another note By default, the text and labels of form elements are
       escaped according to HTML rules.  This means that you can safely use
       "<CLICK ME>" as the label for a button.  However, it also interferes
       with your ability to incorporate special HTML character sequences, such
       as &Aacute;, into your fields.  If you wish to turn off automatic
       escaping, call the autoEscape() method with a false value immediately
       after creating the CGI object:

          $query = new CGI;
          $query->autoEscape(undef);



       CREATING AN ISINDEX TAG

          print $query->isindex(-action=>$action);

                -or-

          print $query->isindex($action);

       Prints out an <ISINDEX> tag.  Not very exciting.  The parameter -action
       specifies the URL of the script to process the query.  The default is
       to process the query with the current script.

       STARTING AND ENDING A FORM

           print $query->startform(-method=>$method,
                                   -action=>$action,
                                   -encoding=>$encoding);
             <... various form stuff ...>
           print $query->endform;

               -or-

           print $query->startform($method,$action,$encoding);
             <... various form stuff ...>
           print $query->endform;

       startform() will return a <FORM> tag with the optional method, action
       and form encoding that you specify.  The defaults are:
           method: POST
           action: this script
           encoding: application/x-www-form-urlencoded

       endform() returns the closing </FORM> tag.

       Startform()'s encoding method tells the browser how to package the
       various fields of the form before sending the form to the server.  Two
       values are possible:

       application/x-www-form-urlencoded
               This is the older type of encoding used by all browsers prior
               to Netscape 2.0.  It is compatible with many CGI scripts and is
               suitable for short fields containing text data.  For your
               convenience, CGI.pm stores the name of this encoding type in
               $CGI::URL_ENCODED.

       multipart/form-data
               This is the newer type of encoding introduced by Netscape 2.0.
               It is suitable for forms that contain very large fields or that
               are intended for transferring binary data.  Most importantly,
               it enables the "file upload" feature of Netscape 2.0 forms.
               For your convenience, CGI.pm stores the name of this encoding
               type in &CGI::MULTIPART

               Forms that use this type of encoding are not easily interpreted
               by CGI scripts unless they use CGI.pm or another library
               designed to handle them.

               For compatibility, the startform() method uses the older form
               of encoding by default.  If you want to use the newer form of
               encoding by default, you can call start_multipart_form()
               instead of startform().

               JAVASCRIPTING: The -name and -onSubmit parameters are provided
               for use with JavaScript.  The -name parameter gives the form a
               name so that it can be identified and manipulated by JavaScript
               functions.  -onSubmit should point to a JavaScript function
               that will be executed just before the form is submitted to your
               server.  You can use this opportunity to check the contents of
               the form for consistency and completeness.  If you find
               something wrong, you can put up an alert box or maybe fix
               things up yourself.  You can abort the submission by returning
               false from this function.

               Usually the bulk of JavaScript functions are defined in a
               <SCRIPT> block in the HTML header and -onSubmit points to one
               of these function call.  See start_html() for details.

       CREATING A TEXT FIELD

           print $query->textfield(-name=>'field_name',
                                   -default=>'starting value',
                                   -size=>50,
                                   -maxlength=>80);
               -or-

           print $query->textfield('field_name','starting value',50,80);

       textfield() will return a text input field.

       Parameters

       1.      The first parameter is the required name for the field (-name).

       2.      The optional second parameter is the default starting value for
               the field contents (-default).

       3.      The optional third parameter is the size of the field in
                     characters (-size).

       4.      The optional fourth parameter is the maximum number of
               characters the
                     field will accept (-maxlength).

               As with all these methods, the field will be initialized with
               its previous contents from earlier invocations of the script.
               When the form is processed, the value of the text field can be
               retrieved with:

                      $value = $query->param('foo');

               If you want to reset it from its initial value after the script
               has been called once, you can do so like this:

                      $query->param('foo',"I'm taking over this value!");

               NEW AS OF VERSION 2.15: If you don't want the field to take on
               its previous value, you can force its current value by using
               the -override (alias -force) parameter:

                   print $query->textfield(-name=>'field_name',
                                           -default=>'starting value',
                                           -override=>1,
                                           -size=>50,
                                           -maxlength=>80);

               JAVASCRIPTING: You can also provide -onChange, -onFocus,
               -onBlur, -onMouseOver, -onMouseOut and -onSelect parameters to
               register JavaScript event handlers.  The onChange handler will
               be called whenever the user changes the contents of the text
               field.  You can do text validation if you like.  onFocus and
               onBlur are called respectively when the insertion point moves
               into and out of the text field.  onSelect is called when the
               user changes the portion of the text that is selected.

       CREATING A BIG TEXT FIELD

          print $query->textarea(-name=>'foo',
                                 -default=>'starting value',
                                 -rows=>10,
                                 -columns=>50);

               -or

          print $query->textarea('foo','starting value',10,50);

       textarea() is just like textfield, but it allows you to specify rows
       and columns for a multiline text entry box.  You can provide a starting
       value for the field, which can be long and contain multiple lines.

       JAVASCRIPTING: The -onChange, -onFocus, -onBlur , -onMouseOver,
       -onMouseOut, and -onSelect parameters are recognized.  See textfield().

       CREATING A PASSWORD FIELD

          print $query->password_field(-name=>'secret',
                                       -value=>'starting value',
                                       -size=>50,
                                       -maxlength=>80);
               -or-

          print $query->password_field('secret','starting value',50,80);

       password_field() is identical to textfield(), except that its contents
       will be starred out on the web page.

       JAVASCRIPTING: The -onChange, -onFocus, -onBlur, -onMouseOver,
       -onMouseOut and -onSelect parameters are recognized.  See textfield().

       CREATING A FILE UPLOAD FIELD

           print $query->filefield(-name=>'uploaded_file',
                                   -default=>'starting value',
                                   -size=>50,
                                   -maxlength=>80);
               -or-

           print $query->filefield('uploaded_file','starting value',50,80);

       filefield() will return a file upload field for Netscape 2.0 browsers.
       In order to take full advantage of this you must use the new multipart
       encoding scheme for the form.  You can do this either by calling
       startform() with an encoding type of $CGI::MULTIPART, or by calling the
       new method start_multipart_form() instead of vanilla startform().

       Parameters

       1.      The first parameter is the required name for the field (-name).

       2.      The optional second parameter is the starting value for the
               field contents to be used as the default file name (-default).

               The beta2 version of Netscape 2.0 currently doesn't pay any
               attention to this field, and so the starting value will always
               be blank.  Worse, the field loses its "sticky" behavior and
               forgets its previous contents.  The starting value field is
               called for in the HTML specification, however, and possibly
               later versions of Netscape will honor it.

       3.      The optional third parameter is the size of the field in
               characters (-size).

       4.      The optional fourth parameter is the maximum number of
               characters the field will accept (-maxlength).

               When the form is processed, you can retrieve the entered
               filename by calling param().

                      $filename = $query->param('uploaded_file');

               In Netscape Navigator 2.0, the filename that gets returned is
               the full local filename on the remote user's machine.  If the
               remote user is on a Unix machine, the filename will follow Unix
               conventions:

                       /path/to/the/file

               On an MS-DOS/Windows and OS/2 machines, the filename will
               follow DOS conventions:

                       C:\PATH\TO\THE\FILE.MSW

               On a Macintosh machine, the filename will follow Mac
               conventions:

                       HD 40:Desktop Folder:Sort Through:Reminders

               The filename returned is also a file handle.  You can read the
               contents of the file using standard Perl file reading calls:

                       # Read a text file and print it out
                       while (<$filename>) {
                          print;
                       }

                       # Copy a binary file to somewhere safe
                       open (OUTFILE,">>/usr/local/web/users/feedback");
                       while ($bytesread=read($filename,$buffer,1024)) {
                          print OUTFILE $buffer;
                       }

               When a file is uploaded the browser usually sends along some
               information along with it in the format of headers.  The
               information usually includes the MIME content type.  Future
               browsers may send other information as well (such as
               modification date and size). To retrieve this information, call
               uploadInfo().  It returns a reference to an associative array
               containing all the document headers.

                      $filename = $query->param('uploaded_file');
                      $type = $query->uploadInfo($filename)->{'Content-Type'};
                      unless ($type eq 'text/html') {
                         die "HTML FILES ONLY!";
                      }

               If you are using a machine that recognizes "text" and "binary"
               data modes, be sure to understand when and how to use them (see
               the Camel book).  Otherwise you may find that binary files are
               corrupted during file uploads.

               JAVASCRIPTING: The -onChange, -onFocus, -onBlur, -onMouseOver,
               -onMouseOut and -onSelect parameters are recognized.  See
               textfield() for details.

       CREATING A POPUP MENU

          print $query->popup_menu('menu_name',
                                   ['eenie','meenie','minie'],
                                   'meenie');

             -or-

          %labels = ('eenie'=>'your first choice',
                     'meenie'=>'your second choice',
                     'minie'=>'your third choice');
          print $query->popup_menu('menu_name',
                                   ['eenie','meenie','minie'],
                                   'meenie',\%labels);

               -or (named parameter style)-

          print $query->popup_menu(-name=>'menu_name',
                                   -values=>['eenie','meenie','minie'],
                                   -default=>'meenie',
                                   -labels=>\%labels);

       popup_menu() creates a menu.

       1.      The required first argument is the menu's name (-name).

       2.      The required second argument (-values) is an array reference
               containing the list of menu items in the menu.  You can pass
               the method an anonymous array, as shown in the example, or a
               reference to a named array, such as "\@foo".

       3.      The optional third parameter (-default) is the name of the
               default menu choice.  If not specified, the first item will be
               the default.  The values of the previous choice will be
               maintained across queries.

       4.      The optional fourth parameter (-labels) is provided for people
               who want to use different values for the user-visible label
               inside the popup menu nd the value returned to your script.
               It's a pointer to an associative array relating menu values to
               user-visible labels.  If you leave this parameter blank, the
               menu values will be displayed by default.  (You can also leave
               a label undefined if you want to).

               When the form is processed, the selected value of the popup
               menu can be retrieved using:

                     $popup_menu_value = $query->param('menu_name');

               JAVASCRIPTING: popup_menu() recognizes the following event
               handlers: -onChange, -onFocus, -onMouseOver, -onMouseOut, and
               -onBlur.  See the textfield() section for details on when these
               handlers are called.

       CREATING A SCROLLING LIST

          print $query->scrolling_list('list_name',
                                       ['eenie','meenie','minie','moe'],
                                       ['eenie','moe'],5,'true');
             -or-

          print $query->scrolling_list('list_name',
                                       ['eenie','meenie','minie','moe'],
                                       ['eenie','moe'],5,'true',
                                       \%labels);

               -or-

          print $query->scrolling_list(-name=>'list_name',
                                       -values=>['eenie','meenie','minie','moe'],
                                       -default=>['eenie','moe'],
                                       -size=>5,
                                       -multiple=>'true',
                                       -labels=>\%labels);

       scrolling_list() creates a scrolling list.

       Parameters:

       1.      The first and second arguments are the list name (-name) and
               values (-values).  As in the popup menu, the second argument
               should be an array reference.

       2.      The optional third argument (-default) can be either a
               reference to a list containing the values to be selected by
               default, or can be a single value to select.  If this argument
               is missing or undefined, then nothing is selected when the list
               first appears.  In the named parameter version, you can use the
               synonym "-defaults" for this parameter.

       3.      The optional fourth argument is the size of the list (-size).

       4.      The optional fifth argument can be set to true to allow
               multiple simultaneous selections (-multiple).  Otherwise only
               one selection will be allowed at a time.

       5.      The optional sixth argument is a pointer to an associative
               array containing long user-visible labels for the list items
               (-labels).  If not provided, the values will be displayed.

               When this form is processed, all selected list items will be
               returned as a list under the parameter name 'list_name'.  The
               values of the selected items can be retrieved with:

                     @selected = $query->param('list_name');


               JAVASCRIPTING: scrolling_list() recognizes the following event
               handlers: -onChange, -onFocus, -onMouseOver, -onMouseOut and
               -onBlur.  See textfield() for the description of when these
               handlers are called.

       CREATING A GROUP OF RELATED CHECKBOXES

          print $query->checkbox_group(-name=>'group_name',
                                       -values=>['eenie','meenie','minie','moe'],
                                       -default=>['eenie','moe'],
                                       -linebreak=>'true',
                                       -labels=>\%labels);

          print $query->checkbox_group('group_name',
                                       ['eenie','meenie','minie','moe'],
                                       ['eenie','moe'],'true',\%labels);

          HTML3-COMPATIBLE BROWSERS ONLY:

          print $query->checkbox_group(-name=>'group_name',
                                       -values=>['eenie','meenie','minie','moe'],
                                       -rows=2,-columns=>2);


       checkbox_group() creates a list of checkboxes that are related by the
       same name.

       Parameters:

       1.      The first and second arguments are the checkbox name and
               values, respectively (-name and -values).  As in the popup
               menu, the second argument should be an array reference.  These
               values are used for the user-readable labels printed next to
               the checkboxes as well as for the values passed to your script
               in the query string.

       2.      The optional third argument (-default) can be either a
               reference to a list containing the values to be checked by
               default, or can be a single value to checked.  If this argument
               is missing or undefined, then nothing is selected when the list
               first appears.

       3.      The optional fourth argument (-linebreak) can be set to true to
               place line breaks between the checkboxes so that they appear as
               a vertical list.  Otherwise, they will be strung together on a
               horizontal line.

       4.      The optional fifth argument is a pointer to an associative
               array relating the checkbox values to the user-visible labels
               that will be printed next to them (-labels).  If not provided,
               the values will be used as the default.

       5.      HTML3-compatible browsers (such as Netscape) can take advantage
               of the optional parameters -rows, and -columns.  These
               parameters cause checkbox_group() to return an HTML3 compatible
               table containing the checkbox group formatted with the
               specified number of rows and columns.  You can provide just the
               -columns parameter if you wish; checkbox_group will calculate
               the correct number of rows for you.

               To include row and column headings in the returned table, you
               can use the -rowheaders and -colheaders parameters.  Both of
               these accept a pointer to an array of headings to use.  The
               headings are just decorative.  They don't reorganize the
               interpretation of the checkboxes -- they're still a single
               named unit.

               When the form is processed, all checked boxes will be returned
               as a list under the parameter name 'group_name'.  The values of
               the "on" checkboxes can be retrieved with:

                     @turned_on = $query->param('group_name');

               The value returned by checkbox_group() is actually an array of
               button elements.  You can capture them and use them within
               tables, lists, or in other creative ways:

                   @h = $query->checkbox_group(-name=>'group_name',-values=>\@values);
                   &use_in_creative_way(@h);

               JAVASCRIPTING: checkbox_group() recognizes the -onClick
               parameter.  This specifies a JavaScript code fragment or
               function call to be executed every time the user clicks on any
               of the buttons in the group.  You can retrieve the identity of
               the particular button clicked on using the "this" variable.

       CREATING A STANDALONE CHECKBOX

           print $query->checkbox(-name=>'checkbox_name',
                                  -checked=>'checked',
                                  -value=>'ON',
                                  -label=>'CLICK ME');

               -or-

           print $query->checkbox('checkbox_name','checked','ON','CLICK ME');

       checkbox() is used to create an isolated checkbox that isn't logically
       related to any others.

       Parameters:

       1.      The first parameter is the required name for the checkbox
               (-name).  It will also be used for the user-readable label
               printed next to the checkbox.

       2.      The optional second parameter (-checked) specifies that the
               checkbox is turned on by default.  Synonyms are -selected and
               -on.

       3.      The optional third parameter (-value) specifies the value of
               the checkbox when it is checked.  If not provided, the word
               "on" is assumed.

       4.      The optional fourth parameter (-label) is the user-readable
               label to be attached to the checkbox.  If not provided, the
               checkbox name is used.

               The value of the checkbox can be retrieved using:

                   $turned_on = $query->param('checkbox_name');

               JAVASCRIPTING: checkbox() recognizes the -onClick parameter.
               See checkbox_group() for further details.

       CREATING A RADIO BUTTON GROUP

          print $query->radio_group(-name=>'group_name',
                                    -values=>['eenie','meenie','minie'],
                                    -default=>'meenie',
                                    -linebreak=>'true',
                                    -labels=>\%labels);

               -or-

          print $query->radio_group('group_name',['eenie','meenie','minie'],
                                                 'meenie','true',\%labels);

          HTML3-COMPATIBLE BROWSERS ONLY:

          print $query->radio_group(-name=>'group_name',
                                    -values=>['eenie','meenie','minie','moe'],
                                    -rows=2,-columns=>2);

       radio_group() creates a set of logically-related radio buttons (turning
       one member of the group on turns the others off)

       Parameters:

       1.      The first argument is the name of the group and is required
               (-name).

       2.      The second argument (-values) is the list of values for the
               radio buttons.  The values and the labels that appear on the
               page are identical.  Pass an array reference in the second
               argument, either using an anonymous array, as shown, or by
               referencing a named array as in "\@foo".

       3.      The optional third parameter (-default) is the name of the
               default button to turn on. If not specified, the first item
               will be the default.  You can provide a nonexistent button
               name, such as "-" to start up with no buttons selected.

       4.      The optional fourth parameter (-linebreak) can be set to 'true'
               to put line breaks between the buttons, creating a vertical
               list.

       5.      The optional fifth parameter (-labels) is a pointer to an
               associative array relating the radio button values to user-
               visible labels to be used in the display.  If not provided, the
               values themselves are displayed.

       6.      HTML3-compatible browsers (such as Netscape) can take advantage
               of the optional parameters -rows, and -columns.  These
               parameters cause radio_group() to return an HTML3 compatible
               table containing the radio group formatted with the specified
               number of rows and columns.  You can provide just the -columns
               parameter if you wish; radio_group will calculate the correct
               number of rows for you.

               To include row and column headings in the returned table, you
               can use the -rowheader and -colheader parameters.  Both of
               these accept a pointer to an array of headings to use.  The
               headings are just decorative.  They don't reorganize the
               interpetation of the radio buttons -- they're still a single
               named unit.

               When the form is processed, the selected radio button can be
               retrieved using:

                     $which_radio_button = $query->param('group_name');

               The value returned by radio_group() is actually an array of
               button elements.  You can capture them and use them within
               tables, lists, or in other creative ways:

                   @h = $query->radio_group(-name=>'group_name',-values=>\@values);
                   &use_in_creative_way(@h);


       CREATING A SUBMIT BUTTON

          print $query->submit(-name=>'button_name',
                               -value=>'value');

               -or-

          print $query->submit('button_name','value');

       submit() will create the query submission button.  Every form should
       have one of these.

       Parameters:

       1.      The first argument (-name) is optional.  You can give the
               button a name if you have several submission buttons in your
               form and you want to distinguish between them.  The name will
               also be used as the user-visible label.  Be aware that a few
               older browsers don't deal with this correctly and never send
               back a value from a button.

       2.      The second argument (-value) is also optional.  This gives the
               button a value that will be passed to your script in the query
               string.

               You can figure out which button was pressed by using different
               values for each one:

                    $which_one = $query->param('button_name');

               JAVASCRIPTING: radio_group() recognizes the -onClick parameter.
               See checkbox_group() for further details.

       CREATING A RESET BUTTON

          print $query->reset

       reset() creates the "reset" button.  Note that it restores the form to
       its value from the last time the script was called, NOT necessarily to
       the defaults.

       CREATING A DEFAULT BUTTON

          print $query->defaults('button_label')

       defaults() creates a button that, when invoked, will cause the form to
       be completely reset to its defaults, wiping out all the changes the
       user ever made.

       CREATING A HIDDEN FIELD

               print $query->hidden(-name=>'hidden_name',
                                    -default=>['value1','value2'...]);

                       -or-

               print $query->hidden('hidden_name','value1','value2'...);

       hidden() produces a text field that can't be seen by the user.  It is
       useful for passing state variable information from one invocation of
       the script to the next.

       Parameters:

       1.      The first argument is required and specifies the name of this
               field (-name).

       2.      The second argument is also required and specifies its value
               (-default).  In the named parameter style of calling, you can
               provide a single value here or a reference to a whole list

               Fetch the value of a hidden field this way:

                    $hidden_value = $query->param('hidden_name');

               Note, that just like all the other form elements, the value of
               a hidden field is "sticky".  If you want to replace a hidden
               field with some other values after the script has been called
               once you'll have to do it manually:

                    $query->param('hidden_name','new','values','here');


       CREATING A CLICKABLE IMAGE BUTTON

            print $query->image_button(-name=>'button_name',
                                       -src=>'/source/URL',
                                       -align=>'MIDDLE');

               -or-

            print $query->image_button('button_name','/source/URL','MIDDLE');

       image_button() produces a clickable image.  When it's clicked on the
       position of the click is returned to your script as "button_name.x" and
       "button_name.y", where "button_name" is the name you've assigned to it.

       JAVASCRIPTING: image_button() recognizes the -onClick parameter.  See
       checkbox_group() for further details.

       Parameters:

       1.      The first argument (-name) is required and specifies the name
               of this field.

       2.      The second argument (-src) is also required and specifies the
               URL

       3. The third option (-align, optional) is an alignment type, and may be
       TOP, BOTTOM or MIDDLE

               Fetch the value of the button this way:
                    $x = $query->param('button_name.x');
                    $y = $query->param('button_name.y');

       CREATING A JAVASCRIPT ACTION BUTTON

            print $query->button(-name=>'button_name',
                                 -value=>'user visible label',
                                 -onClick=>"do_something()");

               -or-

            print $query->button('button_name',"do_something()");

       button() produces a button that is compatible with Netscape 2.0's
       JavaScript.  When it's pressed the fragment of JavaScript code pointed
       to by the -onClick parameter will be executed.  On non-Netscape
       browsers this form element will probably not even display.

NETSCAPE COOKIES
       Netscape browsers versions 1.1 and higher support a so-called "cookie"
       designed to help maintain state within a browser session.  CGI.pm has
       several methods that support cookies.

       A cookie is a name=value pair much like the named parameters in a CGI
       query string.  CGI scripts create one or more cookies and send them to
       the browser in the HTTP header.  The browser maintains a list of
       cookies that belong to a particular Web server, and returns them to the
       CGI script during subsequent interactions.

       In addition to the required name=value pair, each cookie has several
       optional attributes:

       1. an expiration time
               This is a time/date string (in a special GMT format) that
               indicates when a cookie expires.  The cookie will be saved and
               returned to your script until this expiration date is reached
               if the user exits Netscape and restarts it.  If an expiration
               date isn't specified, the cookie will remain active until the
               user quits Netscape.

       2. a domain
               This is a partial or complete domain name for which the cookie
               is valid.  The browser will return the cookie to any host that
               matches the partial domain name.  For example, if you specify a
               domain name of ".capricorn.com", then Netscape will return the
               cookie to Web servers running on any of the machines
               "www.capricorn.com", "www2.capricorn.com",
               "feckless.capricorn.com", etc.  Domain names must contain at
               least two periods to prevent attempts to match on top level
               domains like ".edu".  If no domain is specified, then the
               browser will only return the cookie to servers on the host the
               cookie originated from.

       3. a path
               If you provide a cookie path attribute, the browser will check
               it against your script's URL before returning the cookie.  For
               example, if you specify the path "/cgi-bin", then the cookie
               will be returned to each of the scripts "/cgi-bin/tally.pl",
               "/cgi-bin/order.pl", and "/cgi-
               bin/customer_service/complain.pl", but not to the script "/cgi-
               private/site_admin.pl".  By default, path is set to "/", which
               causes the cookie to be sent to any CGI script on your site.

       4. a """"secure"""" flag
               If the "secure" attribute is set, the cookie will only be sent
               to your script if the CGI request is occurring on a secure
               channel, such as SSL.

               The interface to Netscape cookies is the cookie() method:

                   $cookie = $query->cookie(-name=>'sessionID',
                                            -value=>'xyzzy',
                                            -expires=>'+1h',
                                            -path=>'/cgi-bin/database',
                                            -domain=>'.capricorn.org',
                                            -secure=>1);
                   print $query->header(-cookie=>$cookie);

               cookie() creates a new cookie.  Its parameters include:

       -name   The name of the cookie (required).  This can be any string at
               all.  Although Netscape limits its cookie names to non-
               whitespace alphanumeric characters, CGI.pm removes this
               restriction by escaping and unescaping cookies behind the
               scenes.

       -value  The value of the cookie.  This can be any scalar value, array
               reference, or even associative array reference.  For example,
               you can store an entire associative array into a cookie this
               way:

                       $cookie=$query->cookie(-name=>'family information',
                                              -value=>\%childrens_ages);


       -path   The optional partial path for which this cookie will be valid,
               as described above.

       -domain The optional partial domain for which this cookie will be
               valid, as described above.

       -expires
               The optional expiration date for this cookie.  The format is as
               described in the section on the header() method:

                       "+1h"  one hour from now


       -secure If set to true, this cookie will only be used within a secure
               SSL session.

               The cookie created by cookie() must be incorporated into the
               HTTP header within the string returned by the header() method:

                       print $query->header(-cookie=>$my_cookie);

               To create multiple cookies, give header() an array reference:

                       $cookie1 = $query->cookie(-name=>'riddle_name',
                                                 -value=>"The Sphynx's Question");
                       $cookie2 = $query->cookie(-name=>'answers',
                                                 -value=>\%answers);
                       print $query->header(-cookie=>[$cookie1,$cookie2]);

               To retrieve a cookie, request it by name by calling cookie()
               method without the -value parameter:

                       use CGI;
                       $query = new CGI;
                       %answers = $query->cookie(-name=>'answers');
                       # $query->cookie('answers') will work too!

               The cookie and CGI namespaces are separate.  If you have a
               parameter named 'answers' and a cookie named 'answers', the
               values retrieved by param() and cookie() are independent of
               each other.  However, it's simple to turn a CGI parameter into
               a cookie, and vice-versa:

                  # turn a CGI parameter into a cookie
                  $c=$q->cookie(-name=>'answers',-value=>[$q->param('answers')]);
                  # vice-versa
                  $q->param(-name=>'answers',-value=>[$q->cookie('answers')]);

               See the cookie.cgi example script for some ideas on how to use
               cookies effectively.

               NOTE: There appear to be some (undocumented) restrictions on
               Netscape cookies.  In Netscape 2.01, at least, I haven't been
               able to set more than three cookies at a time.  There may also
               be limits on the length of cookies.  If you need to store a lot
               of information, it's probably better to create a unique session
               ID, store it in a cookie, and use the session ID to locate an
               external file/database saved on the server's side of the
               connection.

WORKING WITH NETSCAPE FRAMES
       It's possible for CGI.pm scripts to write into several browser panels
       and windows using Netscape's frame mechanism.  There are three
       techniques for defining new frames programmatically:

       1. Create a <Frameset> document
               After writing out the HTTP header, instead of creating a
               standard HTML document using the start_html() call, create a
               <FRAMESET> document that defines the frames on the page.
               Specify your script(s) (with appropriate parameters) as the SRC
               for each of the frames.

               There is no specific support for creating <FRAMESET> sections
               in CGI.pm, but the HTML is very simple to write.  See the frame
               documentation in Netscape's home pages for details

                 http://home.netscape.com/assist/net_sites/frames.html


       2. Specify the destination for the document in the HTTP header
               You may provide a -target parameter to the header() method:

                   print $q->header(-target=>'ResultsWindow');

               This will tell Netscape to load the output of your script into
               the frame named "ResultsWindow".  If a frame of that name
               doesn't already exist, Netscape will pop up a new window and
               load your script's document into that.  There are a number of
               magic names that you can use for targets.  See the frame
               documents on Netscape's home pages for details.

       3. Specify the destination for the document in the <FORM> tag
               You can specify the frame to load in the FORM tag itself.  With
               CGI.pm it looks like this:

                   print $q->startform(-target=>'ResultsWindow');

               When your script is reinvoked by the form, its output will be
               loaded into the frame named "ResultsWindow".  If one doesn't
               already exist a new window will be created.

               The script "frameset.cgi" in the examples directory shows one
               way to create pages in which the fill-out form and the response
               live in side-by-side frames.

LIMITED SUPPORT FOR CASCADING STYLE SHEETS
       CGI.pm has limited support for HTML3's cascading style sheets (css).
       To incorporate a stylesheet into your document, pass the start_html()
       method a -style parameter.  The value of this parameter may be a
       scalar, in which case it is incorporated directly into a <STYLE>
       section, or it may be a hash reference.  In the latter case you should
       provide the hash with one or more of -src or -code.  -src points to a
       URL where an externally-defined stylesheet can be found.  -code points
       to a scalar value to be incorporated into a <STYLE> section.  Style
       definitions in -code override similarly-named ones in -src, hence the
       name "cascading."

       You may also specify the type of the stylesheet by adding the optional
       -type parameter to the hash pointed to by -style.  If not specified,
       the style defaults to 'text/css'.

       To refer to a style within the body of your document, add the -class
       parameter to any HTML element:

           print h1({-class=>'Fancy'},'Welcome to the Party');

       Or define styles on the fly with the -style parameter:

           print h1({-style=>'Color: red;'},'Welcome to Hell');

       You may also use the new span() element to apply a style to a section
       of text:

           print span({-style=>'Color: red;'},
                      h1('Welcome to Hell'),
                      "Where did that handbasket get to?"
                      );

       Note that you must import the ":html3" definitions to have the span()
       method available.  Here's a quick and dirty example of using CSS's.
       See the CSS specification at http://www.w3.org/pub/WWW/TR/Wd-css-1.html
       for more information.

           use CGI qw/:standard :html3/;

           #here's a stylesheet incorporated directly into the page
           $newStyle=<<END;
           <!--
           P.Tip {
               margin-right: 50pt;
               margin-left: 50pt;
               color: red;
           }
           P.Alert {
               font-size: 30pt;
               font-family: sans-serif;
             color: red;
           }
           -->
           END
           print header();
           print start_html( -title=>'CGI with Style',
                             -style=>{-src=>'http://www.capricorn.com/style/st1.css',
                                      -code=>$newStyle}
                            );
           print h1('CGI with Style'),
                 p({-class=>'Tip'},
                   "Better read the cascading style sheet spec before playing with this!"),
                 span({-style=>'color: magenta'},
                      "Look Mom, no hands!",
                      p(),
                      "Whooo wee!"
                      );
           print end_html;


DEBUGGING
       If you are running the script from the command line or in the perl
       debugger, you can pass the script a list of keywords or parameter=value
       pairs on the command line or from standard input (you don't have to
       worry about tricking your script into reading from environment
       variables).  You can pass keywords like this:

           your_script.pl keyword1 keyword2 keyword3

       or this:

          your_script.pl keyword1+keyword2+keyword3

       or this:

           your_script.pl name1=value1 name2=value2

       or this:

           your_script.pl name1=value1&name2=value2

       or even as newline-delimited parameters on standard input.

       When debugging, you can use quotes and backslashes to escape characters
       in the familiar shell manner, letting you place spaces and other funny
       characters in your parameter=value pairs:

          your_script.pl "name1='I am a long value'" "name2=two\ words"


       DUMPING OUT ALL THE NAME/VALUE PAIRS

       The dump() method produces a string consisting of all the query's
       name/value pairs formatted nicely as a nested list.  This is useful for
       debugging purposes:

           print $query->dump


       Produces something that looks like:

           <UL>
           <LI>name1
               <UL>
               <LI>value1
               <LI>value2
               </UL>
           <LI>name2
               <UL>
               <LI>value1
               </UL>
           </UL>

       You can pass a value of 'true' to dump() in order to get it to print
       the results out as plain text, suitable for incorporating into a <PRE>
       section.

       As a shortcut, as of version 1.56 you can interpolate the entire CGI
       object into a string and it will be replaced with the a nice HTML dump
       shown above:

           $query=new CGI;
           print "<H2>Current Values</H2> $query\n";


FETCHING ENVIRONMENT VARIABLES
       Some of the more useful environment variables can be fetched through
       this interface.  The methods are as follows:

       accept()
               Return a list of MIME types that the remote browser accepts. If
               you give this method a single argument corresponding to a MIME
               type, as in $query->accept('text/html'), it will return a
               floating point value corresponding to the browser's preference
               for this type from 0.0 (don't want) to 1.0.  Glob types (e.g.
               text/*) in the browser's accept list are handled correctly.

       raw_cookie()
               Returns the HTTP_COOKIE variable, an HTTP extension implemented
               by Netscape browsers version 1.1 and higher.  Cookies have a
               special format, and this method call just returns the raw form
               (?cookie dough).  See cookie() for ways of setting and
               retrieving cooked cookies.

               Called with no parameters, raw_cookie() returns the packed
               cookie structure.  You can separate it into individual cookies
               by splitting on the character sequence "; ".  Called with the
               name of a cookie, retrieves the unescaped form of the cookie.
               You can use the regular cookie() method to get the names, or
               use the raw_fetch() method from the CGI::Cookie module.

       user_agent()
               Returns the HTTP_USER_AGENT variable.  If you give this method
               a single argument, it will attempt to pattern match on it,
               allowing you to do something like $query->user_agent(netscape);

       path_info()
               Returns additional path information from the script URL.  E.G.
               fetching /cgi-bin/your_script/additional/stuff will result in
               $query->path_info() returning "additional/stuff".

               NOTE: The Microsoft Internet Information Server is broken with
               respect to additional path information.  If you use the Perl
               DLL library, the IIS server will attempt to execute the
               additional path information as a Perl script.  If you use the
               ordinary file associations mapping, the path information will
               be present in the environment, but incorrect.  The best thing
               to do is to avoid using additional path information in CGI
               scripts destined for use with IIS.

       path_translated()
               As per path_info() but returns the additional path information
               translated into a physical path, e.g.
               "/usr/local/etc/httpd/htdocs/additional/stuff".

               The Microsoft IIS is broken with respect to the translated path
               as well.

       remote_host()
               Returns either the remote host name or IP address.  if the
               former is unavailable.

       script_name() Return the script name as a partial URL, for self-
       refering scripts.

       referer()
               Return the URL of the page the browser was viewing prior to
               fetching your script.  Not available for all browsers.

       auth_type ()
               Return the authorization/verification method in use for this
               script, if any.

       server_name ()
               Returns the name of the server, usually the machine's host
               name.

       virtual_host ()
               When using virtual hosts, returns the name of the host that the
               browser attempted to contact

       server_software ()
               Returns the server software and version number.

       remote_user ()
               Return the authorization/verification name used for user
               verification, if this script is protected.

       user_name ()
               Attempt to obtain the remote user's name, using a variety of
               different techniques.  This only works with older browsers such
               as Mosaic.  Netscape does not reliably report the user name!

       request_method()
               Returns the method used to access your script, usually one of
               'POST', 'GET' or 'HEAD'.

USING NPH SCRIPTS
       NPH, or "no-parsed-header", scripts bypass the server completely by
       sending the complete HTTP header directly to the browser.  This has
       slight performance benefits, but is of most use for taking advantage of
       HTTP extensions that are not directly supported by your server, such as
       server push and PICS headers.

       Servers use a variety of conventions for designating CGI scripts as
       NPH.  Many Unix servers look at the beginning of the script's name for
       the prefix "nph-".  The Macintosh WebSTAR server and Microsoft's
       Internet Information Server, in contrast, try to decide whether a
       program is an NPH script by examining the first line of script output.

       CGI.pm supports NPH scripts with a special NPH mode.  When in this
       mode, CGI.pm will output the necessary extra header information when
       the header() and redirect() methods are called.

       The Microsoft Internet Information Server requires NPH mode.  As of
       version 2.30, CGI.pm will automatically detect when the script is
       running under IIS and put itself into this mode.  You do not need to do
       this manually, although it won't hurt anything if you do.

       There are a number of ways to put CGI.pm into NPH mode:

       In the use statement
               Simply add the "-nph" pragmato the list of symbols to be
               imported into your script:

                     use CGI qw(:standard -nph)


       By calling the nph() method:
               Call nph() with a non-zero parameter at any point after using
               CGI.pm in your program.

                     CGI->nph(1)


       By using -nph parameters in the header() and redirect()  statements:

                     print $q->header(-nph=>1);


Server Push
       CGI.pm provides three simple functions for producing multipart
       documents of the type needed to implement server push.  These functions
       were graciously provided by Ed Jordan <ed@fidalgo.net>.  To import
       these into your namespace, you must import the ":push" set.  You are
       also advised to put the script into NPH mode and to set $⎪ to 1 to
       avoid buffering problems.

       Here is a simple script that demonstrates server push:

         #!/usr/local/bin/perl
         use CGI qw/:push -nph/;
         $⎪ = 1;
         print multipart_init(-boundary=>'----------------here we go!');
         while (1) {
             print multipart_start(-type=>'text/plain'),
                   "The current time is ",scalar(localtime),"\n",
                   multipart_end;
             sleep 1;
         }

       This script initializes server push by calling multipart_init().  It
       then enters an infinite loop in which it begins a new multipart section
       by calling multipart_start(), prints the current local time, and ends a
       multipart section with multipart_end().  It then sleeps a second, and
       begins again.

       multipart_init()         multipart_init(-boundary=>$boundary);
               Initialize the multipart system.  The -boundary argument
               specifies what MIME boundary string to use to separate parts of
               the document.  If not provided, CGI.pm chooses a reasonable
               boundary for you.

       multipart_start()

                 multipart_start(-type=>$type)

               Start a new part of the multipart document using the specified
               MIME type.  If not specified, text/html is assumed.

       multipart_end()

                 multipart_end()

               End a part.  You must remember to call multipart_end() once for
               each multipart_start().

               Users interested in server push applications should also have a
               look at the CGI::Push module.

Avoiding Denial of Service Attacks
       A potential problem with CGI.pm is that, by default, it attempts to
       process form POSTings no matter how large they are.  A wily hacker
       could attack your site by sending a CGI script a huge POST of many
       megabytes.  CGI.pm will attempt to read the entire POST into a
       variable, growing hugely in size until it runs out of memory.  While
       the script attempts to allocate the memory the system may slow down
       dramatically.  This is a form of denial of service attack.

       Another possible attack is for the remote user to force CGI.pm to
       accept a huge file upload.  CGI.pm will accept the upload and store it
       in a temporary directory even if your script doesn't expect to receive
       an uploaded file.  CGI.pm will delete the file automatically when it
       terminates, but in the meantime the remote user may have filled up the
       server's disk space, causing problems for other programs.

       The best way to avoid denial of service attacks is to limit the amount
       of memory, CPU time and disk space that CGI scripts can use.  Some Web
       servers come with built-in facilities to accomplish this. In other
       cases, you can use the shell limit or ulimit commands to put ceilings
       on CGI resource usage.

       CGI.pm also has some simple built-in protections against denial of
       service attacks, but you must activate them before you can use them.
       These take the form of two global variables in the CGI name space:

       $CGI::POST_MAX
               If set to a non-negative integer, this variable puts a ceiling
               on the size of POSTings, in bytes.  If CGI.pm detects a POST
               that is greater than the ceiling, it will immediately exit with
               an error message.  This value will affect both ordinary POSTs
               and multipart POSTs, meaning that it limits the maximum size of
               file uploads as well.  You should set this to a reasonably high
               value, such as 1 megabyte.

       $CGI::DISABLE_UPLOADS
               If set to a non-zero value, this will disable file uploads
               completely.  Other fill-out form values will work as usual.

               You can use these variables in either of two ways.

       1. On a script-by-script basis
               Set the variable at the top of the script, right after the
               "use" statement:

                   use CGI qw/:standard/;
                   use CGI::Carp 'fatalsToBrowser';
                   $CGI::POST_MAX=1024 * 100;  # max 100K posts
                   $CGI::DISABLE_UPLOADS = 1;  # no uploads


       2. Globally for all scripts
               Open up CGI.pm, find the definitions for $POST_MAX and
               $DISABLE_UPLOADS, and set them to the desired values.  You'll
               find them towards the top of the file in a subroutine named
               initialize_globals().

               Since an attempt to send a POST larger than $POST_MAX bytes
               will cause a fatal error, you might want to use CGI::Carp to
               echo the fatal error message to the browser window as shown in
               the example above.  Otherwise the remote user will see only a
               generic "Internal Server" error message.  See the the CGI::Carp
               manpage manual page for more details.

COMPATIBILITY WITH CGI-LIB.PL
       To make it easier to port existing programs that use cgi-lib.pl the
       compatibility routine "ReadParse" is provided.  Porting is simple:

       OLD VERSION
           require "cgi-lib.pl";
           &ReadParse;
           print "The value of the antique is $in{antique}.\n";

       NEW VERSION
           use CGI;
           CGI::ReadParse
           print "The value of the antique is $in{antique}.\n";

       CGI.pm's ReadParse() routine creates a tied variable named %in, which
       can be accessed to obtain the query variables.  Like ReadParse, you can
       also provide your own variable.  Infrequently used features of
       ReadParse, such as the creation of @in and $in variables, are not
       supported.

       Once you use ReadParse, you can retrieve the query object itself this
       way:

           $q = $in{CGI};
           print $q->textfield(-name=>'wow',
                               -value=>'does this really work?');

       This allows you to start using the more interesting features of CGI.pm
       without rewriting your old scripts from scratch.

AUTHOR INFORMATION
       Copyright 1995-1997, Lincoln D. Stein.  All rights reserved.  It may be
       used and modified freely, but I do request that this copyright notice
       remain attached to the file.  You may modify this module as you wish,
       but if you redistribute a modified version, please attach a note
       listing the modifications you have made.

       Address bug reports and comments to: lstein@genome.wi.mit.edu

CREDITS
       Thanks very much to:

       Matt Heffron (heffron@falstaff.css.beckman.com)

       James Taylor (james.taylor@srs.gov)

       Scott Anguish <sanguish@digifix.com>

       Mike Jewell (mlj3u@virginia.edu)

       Timothy Shimmin (tes@kbs.citri.edu.au)

       Joergen Haegg (jh@axis.se)

       Laurent Delfosse (delfosse@csgrad1.cs.wvu.edu)

       Richard Resnick (applepi1@aol.com)

       Craig Bishop (csb@barwonwater.vic.gov.au)

       Tony Curtis (tc@vcpc.univie.ac.at)

       Tim Bunce (Tim.Bunce@ig.co.uk)

       Tom Christiansen (tchrist@convex.com)

       Andreas Koenig (k@franz.ww.TU-Berlin.DE)

       Tim MacKenzie (Tim.MacKenzie@fulcrum.com.au)

       Kevin B. Hendricks (kbhend@dogwood.tyler.wm.edu)

       Stephen Dahmen (joyfire@inxpress.net)

       Ed Jordan (ed@fidalgo.net)

       David Alan Pisoni (david@cnation.com)

       Doug MacEachern (dougm@opengroup.org)

       Robin Houston (robin@oneworld.org)

       ...and many many more...
               for suggestions and bug fixes.

A COMPLETE EXAMPLE OF A SIMPLE FORM-BASED SCRIPT
               #!/usr/local/bin/perl

               use CGI;

               $query = new CGI;

               print $query->header;
               print $query->start_html("Example CGI.pm Form");
               print "<H1> Example CGI.pm Form</H1>\n";
               &print_prompt($query);
               &do_work($query);
               &print_tail;
               print $query->end_html;

               sub print_prompt {
                  my($query) = @_;

                  print $query->startform;
                  print "<EM>What's your name?</EM><BR>";
                  print $query->textfield('name');
                  print $query->checkbox('Not my real name');

                  print "<P><EM>Where can you find English Sparrows?</EM><BR>";
                  print $query->checkbox_group(
                                        -name=>'Sparrow locations',
                                        -values=>[England,France,Spain,Asia,Hoboken],
                                        -linebreak=>'yes',
                                        -defaults=>[England,Asia]);

                  print "<P><EM>How far can they fly?</EM><BR>",
                       $query->radio_group(
                               -name=>'how far',
                               -values=>['10 ft','1 mile','10 miles','real far'],
                               -default=>'1 mile');

                  print "<P><EM>What's your favorite color?</EM>  ";
                  print $query->popup_menu(-name=>'Color',
                                           -values=>['black','brown','red','yellow'],
                                           -default=>'red');

                  print $query->hidden('Reference','Monty Python and the Holy Grail');

                  print "<P><EM>What have you got there?</EM><BR>";
                  print $query->scrolling_list(
                                -name=>'possessions',
                                -values=>['A Coconut','A Grail','An Icon',
                                          'A Sword','A Ticket'],
                                -size=>5,
                                -multiple=>'true');

                  print "<P><EM>Any parting comments?</EM><BR>";
                  print $query->textarea(-name=>'Comments',
                                         -rows=>10,
                                         -columns=>50);

                  print "<P>",$query->reset;
                  print $query->submit('Action','Shout');
                  print $query->submit('Action','Scream');
                  print $query->endform;
                  print "<HR>\n";
               }

               sub do_work {
                  my($query) = @_;
                  my(@values,$key);

                  print "<H2>Here are the current settings in this form</H2>";

                  foreach $key ($query->param) {
                     print "<STRONG>$key</STRONG> -> ";
                     @values = $query->param($key);
                     print join(", ",@values),"<BR>\n";
                 }
               }

               sub print_tail {
                  print <<END;
               <HR>
               <ADDRESS>Lincoln D. Stein</ADDRESS><BR>
               <A HREF="/">Home Page</A>
               END
               }


BUGS
       This module has grown large and monolithic.  Furthermore it's doing
       many things, such as handling URLs, parsing CGI input, writing HTML,
       etc., that are also done in the LWP modules. It should be discarded in
       favor of the CGI::* modules, but somehow I continue to work on it.

       Note that the code is truly contorted in order to avoid spurious
       warnings when programs are run with the -w switch.

SEE ALSO
       the CGI::Carp manpage, the URI::URL manpage, the CGI::Request manpage,
       the CGI::MiniSvr manpage, the CGI::Base manpage, the CGI::Form manpage,
       the CGI::Apache manpage, the CGI::Switch manpage, the CGI::Push
       manpage, the CGI::Fast manpage














































































































































































































3rd Berkeley Distribution    perl 5.005, patch 02                       CGI(3)