static ItIT<Matches> flexMatchIC_iterator(S pat, S input) {
  L<S> tokPat = javaTokNPunctuation_plusAsterisk(pat), tokInput = javaTokNPunctuation_plusAsterisk(input);
  // fail if crucial words not found (could be optimized more)
  new L<Int> varIndices;
  for (int i = 1; i < l(tokPat); i += 2) {
    S t = tokPat.get(i);
    if (eq(t, "*"))
      varIndices.add(i);
    else if (isIdentifier(t) && !cicAtOddPosition(tokInput, t))
      ret emptyItIt();
  }
  
  // TODO: transform to iterator
  LL<S> spreadInputs = ai_spreadCertainIndices_2(tokPat, tokInput, varIndices);
  
  ret mapI_notNulls(spreadInputs, tok -> {
    new Matches m;
    ret match(pat, tok, m) ? m : null;
  });
}