Well it was confusing for me at first too. I subscribe to the Perl/Gtk2 maillist and asked alot of questions, and ran alot of example code found in their archives. You can download their archives in monthly chunks, and search them for code. muppet in particular has been very helpful explaining the difficult parts of Gtk2. The do statement to use the pixbuf-loader was put on the maillist by Aristotle.
If you are getting into Perl/Gtk2, start getting in the habit of opening the perldoc for whatever widget you are interested in, and look at the top, where the inheritance is shown, and at the bottom where the signals are shown. Most of the tougher problems require you to use an inherited method on the widget, or some clever juggling of the events and signals available to that widget.