static L<S> ai_matrixUnpack(L<S> rels) {
  new L<S> out;
  new Matches m;
  for (S rel : unnull(rels))
    if (swicEwic(rel, "[", "] is", m))
      out.add(m.rest());
    else if (swicEwic(rel, "[", "] is not", m))
      out.add(m.rest() + " not");
  ret out;
}