[mfontani]

... but it does, since perl 5.20, which was released May 27, 2014. More than five years ago.

Here's a short example:

    use 5.020_000;
    use warnings;
    use experimental qw<signatures>;
    # this works:
    say add(2, 3);
    # this dies: Too many arguments for subroutine 'main::add' at ...
    say add(2, 3, 4);
    sub add ($x, $y) {
        $x + $y;
    }