Hi, I'm a little rusty on the old Gtk stuff, but I just want to mention something that may help you further.

You have to be careful with the return value of a delete_event, or any Gtk sub for that matter. Adding a 1 or 0 at the end of the sub can be needed sometimes.

#These are different in a very subtle manner.
$window->signal_connect( 'destroy', sub { Gtk2->main_quit() } );
$window->signal_connect(delete_event => sub { Gtk2->main_quit(); 1;});
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See Gtk delete_event for more details.

From a previous problem like yours on the gtk maillist:

Returns: TRUE to stop other handlers from being invoked for the
event. FALSE to propagate the event further."

.... a return of TRUE from the delete-event
handler means "i handled this event, stop propagation."