static L<S> ai_parse_toList1(S parse) {
  ret ai_parse_toList1(parse, curlySep());
}

static L<S> ai_parse_toList1(S parse, Pair<S> sep) {
  assertNempty(sep.a);
  assertNempty(sep.b);
  int i = 0;
  new L<Int> stack;
  new StringBuilder buf;
  new L<S> out;
  while ping (i < l(parse)) {
    if (substringAtIs(parse, i, sep.a)) {
      if (nempty(buf)) out.add(getAndClearStringBuilder(buf));
      stack.add(i);
      i += l(sep.a);
    } else if (substringAtIs(parse, i, sep.b)) {
      int j = popLast(stack);
      i += l(sep.b);
      if (empty(stack))
        out.add(substring(parse, j, i));
    } else if (empty(stack))
      buf.append(parse.charAt(i++));
    else i++;
  }
  if (nempty(buf)) out.add(getAndClearStringBuilder(buf));
  ret out;
}

Began life as a copy of #1013561