sclass NLStringMatcher_dollarVars_underscores extends StringMatcher {
  // change matches only if returning true
  bool match(S pat, S input, SS matches) {
    SS newMatches = matchDollarVarsIC_underscores(pat, input);
    ret newMatches != null && addMapToMapWithoutOverwritingIC(matches, newMatches);
  }
}