sub by_priority {
    my @prio = (-1 => $a, 1 => $b);
    my @prfx = map { (qr/^$_/)x2 } qw(Organization Service FAQ);

    for(@prfx) {
        return $prio[0] if $prio[1] =~ /$_/;
        push @prio, splice @prio, 0, 2; # swap (-1 => $a) and (1 => $b)
    }

    return 0;
}