I agree... I use WWW::Mechanize all the time for this. You can also use LWP or something to have it manage cookies. Here is a quick code sample for you, to get started:

use strict;
use warnings;
use WWW::Mechanize;
use HTTP::Cookies;

my $mech = WWW::Mechanize->new( agent =>$browser_agent);
$mech->cookie_jar(HTTP::Cookies->new());

$mech->get($url_login);
$mech->form_number($form_number);
$mech->field('username' => $username);
$mech->field('password' => $password);

#Submit the form.. ahoy ahoy
$mech->click();
[download]

Just use Firefox addon Web Developer to lookup the form details with ease... thats my personal preference at least.