This problem was a perl quiz of the week: see http://osdir.com/ml/lang.perl.qotw.quiz-of-the-week/2002-12/msg00000.html.

For individual solutions submitted, see: http://osdir.com/ml/lang.perl.qotw.discuss/2002-11/threads.html and http://osdir.com/ml/lang.perl.qotw.discuss/2002-12/threads.html.