The last one is Gtk object. An example of definition of Gtk object looks like.
Example 4. An example of definition of Gtk object
(define-object GtkExText (GtkEditable) (perl Gtk::ExText) (cast GTK_EXTEXT))
This expression defines GtkExText class whose direct parent is GtkEditable, perl package name is 'Gtk::ExText' and the gtk name is 'GTK_EXTEXT'.
The gtk objects will be cached as well as boxed objects seperately. A garbage collection mechanism has been implemented to release the unused perl variables cache for Gtk Objects. (need details of mechanism, however, I don't read these codes yet....)