use WWW::Mechanize;
    my $m = WWW::Mechanize->new( autocheck => 1 );
$m->get("https://www.bittorrent.com/account/signin");
$mech->submit_form(
           form_name => 3,  #I don't know what is this simply i gave
           fields      => {
           username => "abcd",
           password => "abcd",
                },
               button    => 'Sign In',
     );