Form login is different from HTTP authentication. It's usually done with LWP::Useragent and HTTP::Request::Common like this working example:

#!perl -w

use strict;

use LWP::UserAgent;

use HTTP::Request::Common;

my $ua = LWP::UserAgent->new;

my $request = POST ('http://perlmonks.org', [node=>'showchatmessages',
+ displaytype=>'raw']);

my $response = $ua->request($request);

my $page = $response->content; 

print $page;
[download]

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