use Tk::TextUndo;
use Tie::Tk::Text;
sub Tk::Wizard::_my_text_frame {
#...
 my $t = $frame->Scrolled(
  "TextUndo",
 )->pack;
 if ( $args->{-variable} ) {
  tie @{$args->{-variable}}, 'Tie::Tk::Text', $t;
 }
#...
}