static SS matchDollarVarsIC(S pat, S s) {
  if (s == null) null;
  ret matchDollarVarsIC(pat, parse3_cachedInput(s));
}

static SS matchDollarVarsIC(S pat, LS tokS) {
  if (pat == null || tokS == null) null;
  new L<S> vars;
  S pat2 = dollarVarsToStars(pat, vars);
  new Matches m;
  if (!match3(pat2, tokS, m)) null;
  new SS map;
  for (int i = 0; i < l(m.m); i++) {
    S var = vars.get(i);
    S value = m.get(i);
    S oldValue = map.get(var);
    if (oldValue == null) map.put(var, value);
    else if (neqic(oldValue, value)) null;
  }
  ret map;
}

Began life as a copy of #1010858