my $args =  {
        name       => 'test_form',
        field_list => [
            'username' => {
                type  => 'Text',
                apply => [ { check => qr/^[0-9a-z]*/,
                   message => 'Contains invalid characters' } ]
            }
        ]
    };
    my $form = HTML::FormHandler->new( %$args );
    my $renderedform = $form->render;
    print $renderedform;