# let x = 3;; val x : int = 3 # let y = 5;; val y : int = 5 # let z = x+y;; val z : int = 8 # let x = 1000;; val x : int = 1000 # z;; - : int = 8 # let a = 3 in let b = 5 in a+b;; - : int = 8 # a;; Characters 0-1: a;; ^ Unbound value a