docs: public void poppush( int n, Frame ary, String key) {
      addRef(ary);
      for( int i=0; i<n; i++ ) {
        assert _sp > 0;
        _sp--;
        _fcn[_sp] = subRef(_fcn[_sp]);
        _ary[_sp] = subRef(_ary[_sp], _key[_sp]);
      }
      push(1); _ary[_sp-1] = ary; _key[_sp-1] = key;
      assert check_all_refcnts();
    }