print $q->start_form(
-name    => 'main_form2',
-method  => 'POST',
-action  => 'http://xxx.com/cgi-bin/perforce?&Submit=describe&changenum=$1',
-target  => '_blank',
);
print $q->submit(
-name     => 'submit_form2',
-value    => 'See the change',
);
print $q->end_form;