use Tk;

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

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

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

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

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

MainLoop();

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