svoid rewriteWithDollarVars(S input, S inputPattern, S... outPatterns) {
  SS map = flexMatchDollarVarsIC_first(inputPattern, input);
  if (map == null) ret;
  
  // group it
  emitUnlessEqualTo(input, replaceVars_optRound(inputPattern, map));
  
  // rewrite it
  for (S pat : outPatterns)
    emit(replaceVars_optRound(pat, map));
}