Result is Number1 ^ Number2
    which should be preferred for portability.
The result is of type float if any of the arguments is a float. When an integer is raised to the power of a negative integer, the result type depends on the value of the global flag prefer_rationals. If it is on, it is a rational, otherwise a float. When the exponent is not an integer, the result is of type float.
In coroutining mode, if Number1 or Number2 are uninstantiated, the call to ^/3 is delayed until these variables are instantiated.
Success:
      ^(5, 3, 125).
      ^(-5, 3, -125).
      ^(5, -2, 0.04).
      ^(5, 2.2, 34.493244).
      ^(5.0, 2, 25.0).
Fail:
      ^(1, 2, 3).
      ^(1, 2, 3.0).
      ^(5, 2, r).
Error:
      ^(A, 2, 6).             (Error 4).
      ^(-5, 0.5, X).          (Error 20).
      ^(2 + 3, 2, 25).        (Error 24).