my  $JSNoValdtnOnCancelBack = <<EOJSFUNC;
    if (form._submit.value == 'Cancel') {
       // skip validation since we're cancelling
       return true;
    }
EOJSFUNC

... later ...
  $o .= $form->render(
          template   => {
            type      => 'TT2',
                :::::
          },
          jsfunc    => $JSNoValdtnOnCancelBack,
      );