Win32::GUI is an excellent module for GUI programming on Windows, if you don't mind that it isn't cross platform. It provides most widgets available on Windows as part of the core module; there are a few separate packages available for other controls, such as a Scintilla control. It has a fairly simple interface, and a Visual Basic style event model.

The documentation is mostly complete, and comes with a few simple tutorials. Access to Windows API documentation may be required if you need to perform more advanced operations. The module is based on SourceForge and has a mailing list in case you need help.

I found another thread here with some more info about Perl GUI programming. It also has a list of some GUI builders for some of the toolkits.

Update: Link fixed.