this might not even be cool, but it started as a "I bet you can't do that as a a one-liner" from a cow-worker.

we wanted to turn our usernames into email addresses for our domain, from the NIS database.
It isn't entirely in perl, but it is pretty useful for me :)

ypcat passwd | awk -F: '{print $1}' | perl -p -e' ; chomp; print "$_\@ +domain.local > oneliner.out

hope this helps someone else out there....