[Haskell-cafe] Permutations

[Andrew Coppin]

OK, so here's something just for fun:

Given a list of items, find all possible *unique* permutations of that 
list. (E.g., the input list is explicitly _allowed_ to contain 
duplicates. The output list should not contain any duplicate permutations.)

I've found one simple way to do this, but I'm sure there are multiple 
valid approaches. So let's see what people come up with. ;-)