  func f(a, b, x, y): map {
    ab = $a . "_" . $b;
    xy = $x . "_" . $y;
    return {ab : {"foo" : xy}};
  }
  for (k, v in f($a, $b, $x, $y)) {
    print "k is " . k . "  v is ";
    dump v;
  }

