Function perm
Create a Perm struct from a range or of a set of bounds.
auto auto perm(T...)
(
T stuff
);
Examples
auto p = perm([1,2,3]); // All permutations of [1,2,3].
auto p = perm(5); // All permutations of [0,1,2,3,4].
auto p = perm(-1, 2); // All permutations of [-1, 0, 1].