$mech->submit_form(
        form_name => 'HashForm1',
        fields => {
            login_password => 'username',
            login_username => 'password',
            prefLanguage => '00000000',

        },
        button => "submit",
    );

##</code><code>##

$mech->form_name('HashForm1');
$mech->field("login_username",'username');
$mech->field("login_password",'password');
$mech->field("prefLanguage",00000000);
$mech->submit_form();