static S html_addTargetBlank(S html) {
  L<S> tok = htmlTok(html);
  for (int i = 1; i < l(tok); i += 2) pcall {
    S t = tok.get(i);
    if (isTag(t, "a")) {
      SS map = htmlParams(t);
      if (map.containsKey("href")) {
        map.put("target", "_blank");
        tok.set(i, hopeningTag("a", mapToParams(map)));
      }
    }
  }
  ret join(tok);
}