I'd still recommend Tk. It may seem outdated, but it works, it gets the job done, and there's plenty of documentation and tutorials around. And if you are going to teach a course, and the course's aim is to teach a way to code GUIs, then I think that your toolkit of choice should be well documented, and easy to use first, because it's just a tool to teach your students working with widget toolkits.

There's a good chance, that if your students learn to use Tk, they won't have many problems switching to wx, or GTK, as long as you teach them the basics - separating the presentation and the content, laying out the widgets, using some geometry managers, and so on.

That said, some links that can be useful:

• Perl/Tk chapter from Advanced Perl Programming, User Interfaces with Tk
• User Guide from the module's documentation
• SpecTcl - a GUI builder for Tk, released as open source by ActiveState
• other Perl/Tk stuff

I hope that any of this will be useful to you. All the best, and good luck with the course!

regards,
Luke Jefferson