sub id2path_new {
    my $id = shift;
    return q() unless $id;

    # group of digits
    my $bits = length $id > 6 ? 3 : 2;

    # prepend with 0 digits if necessary
    my $id = ('0' x (3 * $bits - length $id)) . $id;

    my @parts = (
        # leftmost part
        (substr $id, 0, -2 * $bits),
        # subparts
        (substr $id,    -2 * $bits) =~ m{(\d{$bits})}xmsg
    );

    return join q{/}, @parts; 
}