The POD specification has always been a bit vague in some areas and L<> is certainly one of those. But there have been some recent improvements in more rigorously defining POD. Unfortunately, the p5p weekly summary didn't include thread-specific links so you'll probably just have to search the archives. One link that was provided was for joining the "pod-people" e-mail list if you are interested in this type of stuff.

Be prepared for the possibility that the new definition nails down the answer to your question as "you can't". POD was designed with much more emphasis on simplicity than power, so it is easy to find things that POD can only almost do.

        - tye (but my friends call me "Tye")