...
my $seq = $x->GrabKey(
    $k->KeysymToKeycode("z"),
    'AnyModifier', $x->root, 0, 'Asynchronous', 'Asynchronous');

$x->event_handler('queue');
my %event = $x->next_event;
### %event

my $t = AE::timer 0, 1, sub {
    my %event = $x->next_event;
    # %event
};

Gtk2->main;

##</code><code>##

Protocol error: bad 2 (Value); Sequence Number 4
 Opcode (33, 0) = GrabKey
 Bad value 183 (0xb7)
 at ./gtk-treeview-action line 31.