In the original C version of this tutorial, this section described the GtkCombo widget. This widget was deprecated, in GTK+ 2.4, in favour of a much powerful (and less broken) widget, GtkComboBox, which uses the same Model-View-Controller paradigm of other widgets, such as GtkTextView and GtkTreeView.
GTK2-Perl installations using GTK+ >= 2.4 should always use the Gtk2::ComboBox widget.