auto x = ["bob":2, "fred":3]
assert_equal(3, x["fred"])


try {
  auto m = ["bob":2, "fred":3];
  m.at("tom");
  assert_true(false);
} catch (out_of_range e) {
  print("out_of_range")
  assert_true(true);
} catch (e) {
  print("other")
  dump_object(e);
  assert_true(false);
}


assert_equal(["bob":2, "fred":3].at("fred"), 3);