static L<S> tok_surroundWordsWithAngularBrackets(L<S> tok, S... words) {
  Set<S> set = litciset(words);
  for (int i = 1; i < l(tok); i += 2) {
    S t = tok.get(i);
    if (set.contains(t))
      tok.set(i, angleBrackets(t));
  }
  ret tok;
}