static SS simpleMatchTriple_dollarVars(T3<S> pat, T3<S> t) {
  if (pat == null || t == null) null;
  new SS match;
  ret matchDollarVarIC(match, pat.a, t.a)
    && matchDollarVarIC(match, pat.b, t.b)
    && matchDollarVarIC(match, pat.c, t.c) ? match : null;
}