Associative arrays seem to be limited to a single dimension

Associative arrays seem to be limited to a single dimension (On the list Wed, Jan 21, 2009 -- Mike Clemow )

int array[3][3];
// This type of assignment gives an exception
3 @=> array["set"]["value"];
// So does this
3 @=> array["set"][0];
// This type of assignment works but...
[1, 2, 3] @=> array["set"];
// ...accessing values causes an exception
<<< array["set"][0] >>>;