$canvas{'ref'}->CanvasBind("<1>" =>
                  sub{
                        my $screenX = Ev('x');
                        my $screenY = Ev('y');
                        my $x = $canvas{'ref'}->canvasx($screenX);
                        my $y = $canvas{'ref'}->canvasy($screenY);
                        print "($x,$y)\n";
                     });