Check out wxPython and wxPerl (they're both wrappers for the excellent wxWindows GUI toolkit).

I've done a fair bit of work with wxPython recently and have been very impressed. When I was checking around for GUI toolkits I didn't find much documentation for wxPerl so I didn't spend much time on it, but there are some examples around the Monastery that are worth a look:

• wxPerl Tutorial one :: The basics
• WxBrowser - a wxPerl HTML Browser
• wxPerl image handling (short & sweet).

And there's a tutorial on perl.com as well.

Update: I also noticed a link to a Gtk-Perl Tutorial in the tutorials section, anyone used this before?