use WWW::Mechanize;
my $mech = WWW::Mechanize->new();
$mech->get("http://www.thesite.com/members/login.asp");
my $content = $mech->content();

$mech->form_number(1);
$form = $mech->current_form();

$mech->field('username', 'username');
$mech->field('password', 'pass123');
print $form->dump();

$result = $mech->submit();