static SS matchDollarVarsIC_underscores(S pat, S s) {
 pcall {
  if (pat == null || s == null) null;
  new L<S> vars;
  S pat2 = dropSuffix("...", dollarVarsToStars_underscoresWithDollarQ(pat, vars));
  s = dropSuffix("...", s);
  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, "$_q_");
    if (quoted) {
      S value = m.m[i++];
      if (!isQuoted(value)) null;
      var = "$" + substring(var, 4);
      if (!strictPutIC(map, var, unquote(value))) null;
    } else {
      int n = underscoreWordCount(var);
      S value = joinWithSpace(subStringArray(m.m, i, i+n));
      if (!strictPutIC(map, var, value)) null;
      i += n;
    }
  }
  ret map;
 } null;
}

Began life as a copy of #1010862