I'm tinkering with wxGlade at the moment, with a moderate degree of success. Johan Vromans wrote a good article in the summer Perl Review on writing and maintaining GUIs with wxGlade. According to the article, wxGlade will round trip code in the way you describe, although I haven't tried it yet.

Of course, it generates Wx code, which is subject to the caveats on getting Wx to work I mentioned in the thread planetscape already cited.

You may also want to look at this thread on ZooZ - which generates Tk code.