PERL: Merge Sort

MergeSort.PL

# http://rosettacode.org/wiki/Sorting_algorithms/Merge_sort#Perl
sub merge_sort {
    my @x = @_;
    return @x if @x < 2;
    my $m = int @x / 2;
    my @a = merge_sort(@x[0 .. $m - 1]);
    my @b = merge_sort(@x[$m .. $#x]);
    for (@x) {
        $_ = 
        !@a            ? shift @b : 
        !@b            ? shift @a : 
        $a[0] <= $b[0] ? shift @a :
        shift @b;
    }
    @x;
}