This is an excellent and well thought out question. Solid ++. The answer is, you haven't done anything wrong. The documentation is a little unclear on this point, but certain Perl operators are overridable, and certain others aren't. In perl 5.6.0 and earlier, chomp was not overridable. So nothing you can do will get your subroutine to be called in place of the built-in.

However, our very own ctweten noticed this in September and discovered that there's no reason at all chomp (and chop) shouldn't be overridable, and patched perl to make that possible. This change was too late for 5.6.0, but is in 5.7.0 and has been integrated into the 5.6.1 trial release 1. So, pending something horrifically bizarre, your first test module should work just fine on 5.6.1.

In the meantime, I would suggest playing around with a different operator to learn how to overload built-ins. If you're interested and have a copy of the source for your version of perl sitting around, the way to figure out what's overridable is by this one-liner, courtesy Nick Ing-Simmons:

perl -ne 'print "$1\n" if /return\s*KEY_(\w+)/' toke.c

Hope this is helpful. Keep up the good work.

-dlc