$setup = sub{
    my $mw = shift;
    $mw->bind('all','<Motion>',$motion); # could be <Enter> as well
    $mw->bind('all','<MouseWheel>',[$mousewheel_event, Tk::Ev('D')]);
    $mw->bind('all','<4>',[$mousewheel_event, 120]);
    $mw->bind('all','<5>',[$mousewheel_event, -120]);
};