// tok must come from htmlTok
// returns index of closing tag or l(tok)
static int findClosingTag(LS tok, int iOpeningTag) {
  S tag = getTag(tok.get(iOpeningTag));
  S closingTag = "/" + tag;
  ifdef findClosingTag_debug
    print("findClosingTag: tag=" + tag);
  endifdef
  int level = 1;
  for (int i = iOpeningTag+2; i < l(tok); i += 2) {
    S t = tok.get(i);
    S tag2 = getTag(t);
    ifdef findClosingTag_debug
      printVars_str("findClosingTag", +tag2, +t);
    endifdef
    if (eqic(tag2, tag))
      ++level;
    else if (eqic(tag2, closingTag)) {
      --level;
      ifdef findClosingTag_debug
        printVars_str("findClosingTag", +level);
      endifdef
      if (level == 0)
        ret i;
    }
  }
  ret l(tok);
}

Began life as a copy of #1007927