Emptying a Table

[kerrang]

Here's a challenge for you

Fred = {}
Fred['barney'] = {}
Fred['barney']['wilma'] = "Flintstone"
Fred = nil
Fred = {}
Fred['barney'] = {}

What does Fred['barney']['wilma'] now contain

Clue: It's not nil, "" nor does it not exist

How does one actually empty a table then?