Here's what I would do.

1. Download the page with the form you want to your computer.

2. Delete the part in the form where it says action="example.php (or whatever)" and put in "formpairs.pl (saved in the same location or whatever)". The script below is formpairs.pl.

#!/usr/bin/perl

# formpairs.pl - extract names and values from HTTP requests

use strict;
use warnings;

my $data; 
if(! $ENV{'REQUEST_METHOD'}) { # not run as a CGI 
  die "Usage: $0 \"url\"\n" unless $ARGV[0]; 
  $data = $ARGV[0]; 
  $data = $1 if $data =~ s/^\w+\:.*?\?(.+)//; 
  print "Data from that URL:\n(\n"; 
} elsif($ENV{'REQUEST_METHOD'} eq 'POST') { 
  read(STDIN, $data, $ENV{'CONTENT_LENGTH'}); 
  print "Content-type: text/plain\n\nPOST data:\n(\n"; 
} else { 
  $data = $ENV{'QUERY_STRING'}; 
  print "Content-type: text/plain\n\nGET data:\n(\n"; 
} 
for (split '&', $data, -1) {   # Assumes proper URLencoded input 
  tr/+/ /;   s/"/\\"/g;   s/=/\" => \"/;   s/%20/ /g; 
  s/%/\\x/g;  # so %0d => \x0d 
  print "  \"$_\",\n"; 
} 
print ")\n";
__END__
[download]

3. Open the page up in your browser locally, and then run the code by submitting the form.

4. This should show you what values you need in your form.

Also check out Perl & LWP by Sean Burke. That's where this code was taken from.

From there I use $mech->set_fields(); to input the form info.

Have fun spamming Myspace! ;)