Re^5: my $cache = undef if undef;

[Aristotle]

If you look a few nodes further up the thread you'll see I'm advising against its use anyway. :-) I'm simply saying that there is a lot of inertia against its disappearance. That's not a promise, of course. It does work in the meantime though, and can very occasionally be useful so long as we're talking about throwaway code (I used it in a oneliner once to save a few keystrokes.)