Maybe think of it this way (as I understand it) 'undef' isn't a value and it isn't a non-value either, it's nothing. it's just a new keyword, a
syntactically somewhat less intuative way of defining a 'delete' operator on the one hand and a "key 'in' table" operator on the other hand to test it's existance (even if nil)
I don't care much about syntax, tough. Semantically I consider it a hugh improvement.
Kind regards, Axel