static WebNode webs_tripleSearch_dollarX_first(S a, S b, S c, Collection<Web> webs) {
  bool isA = eq(a, "$X");
  for (Web web : webs) {
    Pair<WebNode> p = web_matchTriple_dollarVars(a, b, c, web);
    if (p != null)
      ret isA ? p.a : p.b;
  }
  null;
}

static WebNode webs_tripleSearch_dollarX_first(Collection<Web> webs, T3<S> t) {
  ret webs_tripleSearch_dollarX_first(t.a, t.b, t.c, webs);
}