static L<S> dropLeadingPunctuation_keep = ll("*", "<", ">", "(", "{", "[");

static L<S> dropLeadingPunctuation(L<S> tok) {
  tok = new ArrayList<S>(tok);
  for (int i = 1; i < l(tok); ) {
    S t = tok.get(i);
    if (eq(t, "...") || t.length() == 1 && !Character.isLetterOrDigit(t.charAt(0)) && !dropLeadingPunctuation_keep.contains(t)) {
      tok.remove(i);
      tok.remove(i);
    } else break;
  }
  return tok;
}

static S dropLeadingPunctuation(S s) {
  ret join(dropLeadingPunctuation(nlTok(s)));
}