a.b <=> (a b) a!b <=> (a 'b)
(= a (obj a 1 b 3)) a.a ; Error: "reference to undefined identifier: _a"
arc> (= a (obj a 1 b 3)) #hash((b . 3) (a . 1)) arc> a.a nil
arc> a.x Error: "reference to undefined identifier: _x" arc> (let x 'foo a.x) nil
-----