It sounds like you, as a beginner, my want to reconsider your design. The first thing I have to say, is why do you need the overlapping secondary sub-canvases? If you can make something on your sub-canvas, you can do the same thing on the underlying canvas. You can still put a background image on the main canvas, then instead of overlaying other canvases, why not create rectangular regions on the base canvas? In any event, look at this example:

#!/usr/bin/perl
use warnings;
use strict;
use Tk;

my $mw = new MainWindow;

my $main = $mw -> Scrolled("Canvas",-scrollbars=>'e')-> 
          pack(-side =>'left', -fill => 'both', -expand => 1);

my $canvas = $main->Subwidget("canvas");

Tk::bind($canvas, '<MouseWheel>', [ sub {$canvas->yview('scroll',
    -($_[1] / 120) * 3,'units')}, Ev('D')]); 

my $see = "\nHaaa, See that and scroll!";

my $info = $main->createText(180, 15, -text => "$see", 
                    -font => 'Arial 11 bold' , -fill => 'red');

$main->configure(-scrollregion => [0,0,2000 , 2000]);

my $canvas_cube = $main->Canvas(-width => 45, -height => 45, 
                                          -background => 'green');

my $canvasWindow = $main->createWindow(75,75, -window => $canvas_cube)
+;

Tk::bind( $canvas_cube,  '<Enter>' => sub { print "Enter\n"; });
Tk::bind( $canvas_cube,  '<Leave>' => sub { print "Leave\n"; });

Tk::bind( $canvas_cube,  '<Button-1>' => sub { print "1\n"; });

$canvas->focus;

MainLoop;
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