problme when trying to use mouse wheel for scrolling in a canvas

I would like to use the central mouse wheel to scroll on a canvas.  I am
running under windows (XP).  Attached is some test code.
 
 
use Tk;
 
use strict "vars";
 
my ($mw_Main, $canvas, $real_canvas);
 
# sub to add centre wheel of mouse for scrolling
 
sub BindMouseWheel {
 
    my($w) = @_;
 
    if ($^O eq 'MSWin32') {
        $w->CanvasBind('<MouseWheel>' =>
            [ sub { $_[0]->yview('scroll', -($_[1] / 120) * 3, 'units')
},
                Ev('D') ]
        );
    } else {
 
# other o/s code was here
 
    }
}
 
 
$mw_Main = MainWindow->new;
 
$canvas = $mw_Main->Scrolled("Canvas",
                                                -width                =>
300,
                                                -height              =>
300,
                                                -xscrollincrement => 5,
                                                -yscrollincrement => 5,
                                                -scrollregion       =>
[0,0,500,500],
                                    )->pack();
 
$real_canvas = $canvas->Subwidget("canvas");
 
$real_canvas->createLine(0,0, 499, 499);
$real_canvas->createLine(0, 499, 499, 0);
 
BindMouseWheel($real_canvas);
 
 
MainLoop;
 
 
The test code creates a scrolled canvas area and draws a diagonal cross
between the corners.
 
It then calls the sub BindMouseWheel which is exactly as in Mastering
Perl/Tk except that bind has been changed to CanvasBind.
 
Sadly nothing happens when I use the mouse wheel - I had hoped that the
picture (cross) in the canvas would scroll up and down.
 
Is it possible to use the mouse wheel to scroll in a canvas?  If so
could someone:
1.	explain how to amend the test code so that this works;
2.	give the Perl code so that (if possible) the mouse wheel (that
can be moved from side to side and does give a horizontal scroll in
other applications) can be used to scroll in the x direction as well.
 
Best regards
 
Henry Merryweather