(quoted from Darren)

One thing I would like to be able to do is this:

  @baz = cross([1,2],[3,4]); # yields ([1,3],[1,4],[2,3],[2,4])

And alternately, this:

  for cross([1,2],[3,4]) -> $foo,$bar { ... } # loop has 4 iterations

More examples:

  cross() # yields ()
  cross([],[1]) # yields ()
  cross([1,2]) # yields ([1],[2])
  cross([1,2],[3]); # yields ([1,3],[2,3])
  cross([1],[2],[3]) # yields ([1,2,3])
  cross([1],[2],[3,4]) # yields ([1,2,3],[1,2,4])