Visual basic offers impressive RAD that perl can't always match in terms of gui development (caveats : GUILoft, wxDesigner, but I don't think they measure up yet), along with Delphi and the other 'smaller' gui-oriented languages that have stayed the course.

Have you tried glade (the Gtk/Gnome gui builder) + Gtk::GladeXML? I have found it to be very nice with the benefit that the interface description files produced by glade can be used by any number of languages.