static SS matchDollarVarsIC_underscores(S pat, S s) {
  if (pat == null || s == null) null;
  new L<S> vars;
  S pat2 = dollarVarsToStars_underscores(pat, vars);
  new Matches m;
  if (!match(pat2, s, m)) null;
  new SS map;
  int v = 0;
  for (int i = 0; i < l(m.m); ) {
    S var = vars.get(v++);
    bool quoted = startsWith(var, "$_q_");
    S value = joinWithSpace(subStringArray(m.m, i, i+n));
    if (quoted) {
      if (!isQuoted(value)) null;
      var = "$" + substring(var, 4);
    }
    int n = underscoreWordCount(var);
    if (!strictPutIC(map, var, value)) null;
    i += n;
  }
  ret map;
}