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