// returns null if crucial word not found in input
static L<Int> flexMatchIC_getVarIndices(LS tokPat, LS tokInput) {
  // 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)) {
      //print("Crucial word fail (" + t + "): " + pat + " / " + join(tokInput));
      null;
    }
  }
  ret varIndices;
}