i remembered a quotation of a former prof of mine:
To paraphrase Samuel Johnson, we advise you to look over your code very carefully, and whenever you find a part that you think is particularly fine, strike it out!
Charniak et al. 1980
the code you posted is not the easiest one. plus, you are a skilled perler. plus, the language we speak about is perl (everything just is condensed). plus, you said yourself that you are unsure about the expresiveness of the code.
i think, everyone reading that in a few months will get problems - it is then a matter of experience how long the remembering-phase will take to start ;-)