Check out this script for what environment variables are set. It's nice for debugging, but don't keep it on your server.

#!/usr/bin/perl -w

use CGI qw(header start_html end_html);
print header(),start_html();
print "$_ = $ENV{$_}<br>" foreach (keys %ENV);
print "\$0 is $0";
print end_html();
[download]

Of course, you could just use CGI and use its url() or script_name() methods. For more on the syntax for the url() method, check out this link.

antirice    
The first rule of Perl club is - use Perl
The ith rule of Perl club is - follow rule i - 1 for i > 1