You'll get a nack for what works when asking questions. As an exercise, read other's questions and try to answer them (you don't have to answer, if you don't want). You'll quickly see how to think like someone trying answer a question - and what they need to answer it quickly.

What I would've done asking this question: Go to the data. You want to look inside %words. So I would have posted the sub classify which uses %words and the TIE that starts the hash %words. The problem being is you're asking at a perl site - so you should figure some of us have an understanding of perl. But we don't know your data.

To your question:
Take the keys of the %words and split them on '-'.

## UNTESTED
use Data::Dumper;
my %cats;
foreach my $cat_word (keys %words) {
  my ($cat,$word) = split(/-/,$cat_word);
  push(@{$cats{$cat}},$word);
}
print Dumper \%cats;
[download]

There you should have a hash %cats with the words that are in each cat.

As for adding that into your program and printing it nicer than Data::Dumper, I'll leave that up to you.