#!/usr/bin/perl -w
                                                                                
# Strict
use strict;
use warnings;
                                                                                
# Libraries
use Tk;
                                                                                
# Subroutines
sub random($) { int rand $_[0] }

sub random_square($) {
    my $can = shift;
    my ($x0, $y0, $x1, $y1) = (random 256, random 256, random 256, random 256);
    $x1 += $x0; $y1 += $y0;
    my $bg = sprintf "#%02x%02x%02x", random 256, random 256, random 256;
    $can->createRectangle($x0, $y0, $x1, $y1, -fill => $bg);
}

# Main program
my $mw = new MainWindow(-title => "Canvas binding test");
my $can = $mw->Canvas(-bg => 'white', -width => 512, -height => 512);
$can->pack(-expand => 1, -fill => 'both');
$can->CanvasBind('<Configure>', [\&random_square]);
MainLoop;