Thank you both for this example! I think it will help me move much of this kind of stuff away from accessors.

Now that you have mentioned this, I seem to remember something similar being mentioned in that talk, but only as "What he really wants are coercions", but that mention wasn't made loud or raised for discussion. In any case, your posts showed me how Moo* wants to be used for building nicer constructors and how I can eliminate the bad part of my constructors without resorting to the real manual parsing of the constructor arguments again.