def prepend_all(stack, list):
    """
    Prepend all of the items in the given stack onto the head of the
    given list.  (Naturally tail-recursive.)

    For example:

        prepend_all([3, 2, 1], [4, 5]) -> [1, 2, 3, 4, 5]
    """
    if stack == ():
        return list
    else:
        head, tail = stack
        return prepend_all(tail, (head, list))