Perl in a Nutshell, 2nd Edition

Chapter 10. The CGI.pm Module

CGI.pm is a Perl module for creating and parsing CGI forms. It has been distributed with the Perl source kit since 5.004, but you can upgrade your existing CGI.pm installation from CPAN. As of the writing of this edition, the current version of CGI.pm is 2.81.

CGI is an object-oriented module. Don’t let the object-oriented nature scare you off, though; CGI.pm is very easy to use, as evidenced by its overwhelming popularity among all levels of Perl programmers. To give you an idea of how easy it is to use CGI.pm, let’s take a scenario in which a user fills out and submits a form containing her birthday. Without CGI.pm, the script would have to translate the URL-encoded input by hand (probably using a series of regular expressions) and assign it to a variable. For example, you might try an antiquated parsing method like this:

#!/usr/local/bin/perl # CGI script without CGI.pm $size_of_form_info = $ENV{'CONTENT_LENGTH'}; read ($STDIN, $form_info, $size_of_form_info); # Split up each pair of key/value pairs foreach $pair (split (/&/, $form_info)) { # For each pair, split into $key and $value variables ($key, $value) = split (/=/, $pair); # Get rid of the pesky %xx encodings $key =~ s/%([\dA-Fa-f][\dA-Fa-f])/pack ("C", hex ($1))/eg; $value =~ s/%([\dA-Fa-f][\dA-Fa-f])/pack ("C", hex ($1))/eg; # Use $key as index for $parameters hash, $value as value $parameters{$key} = $value; } # Print out the obligatory content type line print "Content-type: text/plain\n\n"; ...