stephen,
I came across this thread, and you post, when looking for some help in doing a diff on the keys between two hashes.

Although code didn't answer my question directly it did give me the insiration to come up with the following:

perl -le '%foo = (1,1, 2,2, 3,3); %bar = (2,2, 3,3); print map { $_ if
+ !$bar{$_} } keys %foo;'
[download]

If you run this code you'll see that only "1" get printed.

Not the most robust piece of code ever, but I came up with it off my own back and it does a job for me. So cheers for the insiration!

!unlike

I write my Perl code like how I like my sex: fast and dirty. ;)