sub o {
  my ($a, $w) = @_;
  my %m; @m{@$a} = 1..@$a;
  my $k = join "", map {sprintf "\\%03o", ord $_} keys %m;
  my $v = join "", map {sprintf "\\%03o", $_ } values %m;
  map { eval "tr/$v/$k/"; $_ } sort map { eval "tr/$k/$v/"; $_ } @$w;
}