That's a pity ... I thought the undef function was supposed to return PL_undef if you passed it no parameters. At least, that's what the Perl cookbook implies on p369, as well as the Camel in its discussion of the undef function in the Appendices. Why wouldn't it work? (And, yes, I'm scared of spelunking the Perl codebase.)
Being right, does not endow the right to be rude; politeness costs nothing.
Being unknowing, is not the same as being stupid.
Expressing a contrary opinion, whether to the individual or the group, is more often a sign of deeper thought than of cantankerous belligerence.
Do not mistake your goals as the only goals; your opinion as the only opinion; your confidence as correctness. Saying you know better is not the same as explaining you know better.