One minor nit: You missed a way to get a false-but-defined value. It's possible if you've set $/=\1, that is, if you're reading a byte at a time.

Actually... and I'm glad you brought this up because I meant to comment on it...

No. Not in 5.004_04. That feature was introduced sometime in 5.005, so the definedness bug could never have been activated by it.

-sauoq
"My two cents aren't worth a dime.";