I couldn't get your example to work, but if you use the 'Array' type it works. There's a catch though: All the elements and subelements have to be the same type. Example:
Foo:Array = [[1, 2, 3], [1, 2, 3]] 'OK! Foo:Array = [["A", "B", "C"], [1, 2, 3]] 'Not OK