use Gtk2::NotificationBubble;
use Gtk2::TrayIcon;
Gtk2->init;

my $icon= Gtk2::TrayIcon->new("test");
my $label= Gtk2::Label->new("test");
$icon->add($label);
$icon->show_all;

my $bubble = Gtk2::NotificationBubble->new;
$bubble->attach($icon);
$bubble->set("Hello", undef, "I'm a bubble!");
$bubble->show(5000);

Gtk2->main;