In coroutining mode, if Number1 or Number2 are free variables, the call to <</3 is delayed until these variables are instantiated.
Success: <<(1, 3, 8). Fail: <<(1, 2, 3). Error: <<(A, 2, 6). (Error 4). <<(6, 2.0, 24.0). (Error 5). <<(4 + 2, 2, 24). (Error 24). <<(5, 2, r). (Error 24).