my $mw = new Tk::MainWindow;
my $top = $mw->Frame->pack;
my $bottom = $mw->Frame->pack;
my @cb = ((map { $top->Checkbutton(-text => $_)->pack(-side => 'left') }
	   qw{Red Green Blue}),
	  (map { $bottom->Checkbutton(-text => $_)->pack(-side => 'left') }
	   qw{Mustard Vinegar Salt}));
MainLoop;