Filling out a web form is very easy to do with WWW::Mechanize - it allows you to specify values for fields, almost like a real browser :

use WWW::Mechanize;
my $url = "http://your.messenger.com/"
my $a = WWW::Mechanize->new();

$a->get($url);

$a->follow_link( text_regex => qr/enter data/i );

$a->submit_form(
    form_number => 3,
    fields      => {
            username    => 'yourname',
            password    => 'secret',
            message     => 'hello world!',
            }
    );
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perl -MHTTP::Daemon -MHTTP::Response -MLWP::Simple -e ' ;    # The  
$d = new HTTP::Daemon and fork and getprint $d->url and exit;#spider
($c = $d->accept())->get_request(); $c->send_response( new   #in the
HTTP::Response(200,$_,$_,qq(Just another Perl hacker\n))); ' #  web
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use LWP::UserAgent;
my $ua = LWP::UserAgent->new(timeout=>45); 
 my $req = POST 'http://myhost.com/cgi-bin/script.pl', 
  [id => '4301330018817403', 
  total_amount => "$grand_total", 
  location => 'hawaii', 
 ]; 
 
my $content = $ua->request($req)->as_string;
[download]