static boolean nlMatch(S pat, S nl, Map<S, Lisp> matches) {

  matches.clear();

  ret nlMatch_sub(nlParse/*_cached*/(pat), nlParse(nl), matches);

}

static boolean nlMatch(Lisp pat, S nl, Map<S, Lisp> matches) {

  matches.clear();

  ret nlMatch_sub(pat, nlParse(nl), matches);

}

static boolean nlMatch(S pat, Lisp nl, Map<S, Lisp> matches) {

  matches.clear();

  ret nlMatch_sub(nlParse/*_cached*/(pat), nl, matches);

}

static boolean nlMatch(Lisp pat, Lisp nl, Map<S, Lisp> matches) {

  matches.clear();

  ret nlMatch_sub(pat, nl, matches);

}

static boolean nlMatch_sub(Lisp pat, Lisp nl, Map<S, Lisp> m) {

  if (pat == null || nl == null) ret false;

  if (pat.isA("*"))

    ret true;

  if (nlIsVar(pat))

    ret nlMatch_putMatch(m, pat.head, nl);

  if (neq(pat.head, nl.head)) ret false;

  // heads identical, proceed to children

  int n = pat.size();

  if (n != nl.size()) ret false;

  for (int i = 0; i < n; i++)

    if (!nlMatch_sub(pat.get(i), nl.get(i), m))

      ret false;

  ret true;

}

static boolean nlMatch_putMatch(Map<S, Lisp> matches, S key, Lisp val) {

  key = dropPrefix("$", key);

  if (matches.containsKey(key) && neq(matches.get(key), val))

    fail("multi-matching not implemented");

  matches.put(key, val);

  ret true;

}