Re: fun with hashes!

Don't know if this falls into categories already
covered (set of active objects in a class? counting?),
but I often find a hash of open filehandles useful.  e.g. to
divide a big file into several smaller ones, using the
distinct values of one of the fields as filenames :

perl -MIO::File -ane '($fds{$F[1]} ||= IO::File->new(">$F[1]"))->print($_)' < bigfile

Brian