use Tk;

$window = MainWindow->new(-background => 'white');

$window->Button(-text => 'Red',
		  -command => sub { colorset('red') })->pack(-side => 'bottom');

$window->Button(-text => 'Blue',
		  -command => sub { colorset('blue') })->pack(-side => 'right');

$window->Button(-text => 'Green',
		  -command => sub { colorset('green') })->pack(-side => 'left');

$window->Button(-text => 'Quit',
		  -command => sub { exit() })->pack(-side => 'top');

MainLoop();

sub colorset {
	$color = shift();
	$window->configure(-background => $color);
}