Some notes:

• X11::Fvwm is not really a GUI library, just a module to get access to fvwm-specific functions. It is not possible to build a GUI application with X11::Fvwm only.
• X11::Protocol got a recent update, but given the simplicity of this module I would consider X11::Protocol to be rock stable for all times :-)
• The Perl/Tk FAQ is still maintained and updated, though there's a lot of historical information in it which should really be removed.