my $btn = Gtk::Button->new("Quit");
$btn->signal_connect(clicked => sub { Gtk->exit(0); return });
$btn->show;

my $window = Gtk::Window->new("toplevel");
$window->signal_connect(delete => sub { Gtk->exit(0); return });
$window->set_title("Test");
$window->border_width(15);
$window->add($btn);
$window->show;