sub i {
    my ($a, $b, $c, $d, $e, $f, $g, $h) = @pack;
    @pack = ($e, $a, $f, $b, $g, $c, $h, $d);
}

sub o {
    my ($a, $b, $c, $d, $e, $f, $g, $h) = @pack;
    @pack = ($a, $e, $b, $f, $c, $g, $d, $h);
}