From README

This module provides perl access to Glib and GLib's GObject libraries.
GLib is a portability and utility library; GObject provides a generic
type system with inheritance and a powerful signal system.  Together
these libraries are used as the foundation for many of the libraries
that make up the Gnome environment, and are used in many unrelated
projects.

This wrapper attempts to provide a perlish interface while remaining
as true as possible to the underlying C API, so that any reference
materials you can find on using GLib may still apply to using the
libraries from perl.  Where GLib's functionality overlaps perl's,
perl's is favored; for example, you will find perl lists and arrays in
place of GSList or GList objects.  Some concepts have been eliminated;
you need never worry about reference-counting on GObjects or GBoxed
structures.  Other concepts have been converted to a perlish analogy;
the GType id will never be seen in perl, as the package name serves
that purpose.  [FIXME link to a document describing this stuff in detail.]

WWW: http://gtk2-perl.sourceforge.net/