3.2.126 reverse

reverse 

LIST

In list context, this function returns a list value consisting of the elements of LIST in the opposite order. This is fairly efficient because it just swaps the pointers around. The function can be used to create descending sequences:

for (reverse 1 .. 10) { ... }

Because of the way hashes flatten into lists when passed to (non-hash-aware) functions, reverse can also be used to invert a hash, presuming the values are unique:

%barfoo = reverse %foobar;

In scalar context, the function concatenates all the elements of LIST together and then returns the reverse of that, character by character.

A small hint: reversing a list sorted earlier by a user-defined function can sometimes be achieved more easily by simply sorting in the opposite direction in the first place.