use Tk;
use Tk::TextUndo;


package Tk::TextUndo;
sub InsertKeypress
{
 my ($w,$char)=@_;
 return if $char eq '';
 if ($char =~ /^\S$/ and !$w->OverstrikeMode and !$w->tagRanges('sel'))
  {
   my $index = $w->index('insert');
   my $undo_item = $w->getUndoAtIndex(-1);
   if (defined($undo_item) &&
       ($undo_item->[0] eq 'delete') &&
       ($undo_item->[2] == $index)
      )
    {
     $w->SUPER::insert($index,$char);
     $undo_item->[2] = $w->index('insert');
     $w->see('insert');         #######ergaenzt
     return;
    }
  }
 $w->addGlobStart;
 $w->SUPER::InsertKeypress($char);
 $w->addGlobEnd;
}
package main;


my $mw = tkinit;

my $testundo = $mw-> Scrolled ('TextUndo', -wrap => 'none',)-> pack ();

MainLoop;