static L<S> splitAtArrow(S s) {
  L<S> tok = javaTok(s);
  new L<S> l;
  int i = 0;
  while (i < l(tok)) {
    int j = indexOfSubList(tok, ll("=", "", ">"), i);
    if (i >= l(tok)) break;
    if (j < 0) j = l(tok);
    l.add(join(tok.subList(i, j)));
    i = j+3;
  }
  ret l;
}