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!',
			}
    );