This may not be too useful by itself, but the implementation is very interesting, because it is short (only 30 lines), it requires a large number of less-well-known Perl features, and its use of those features is not too tricky. So studying the implementation of this module is a great way to learn a several advanced features of Perl at once.
In the past, I would have posted it here, but now that I have a blog, I posted it on my blog. But I thought some of you folks would be interested anyway, so I'm announcing it here.
Here it is. Enjoy!