fvar(func_old_blk_body, func_old_blk_func)
  func_old_blk_body = block.cur()
  block.select(block.reggen())
  if(isset(BLK_FUNC))
    func_old_blk_func = BLK_FUNC
  else
    gvar(BLK_FUNC)
  end
  BLK_FUNC = block.reggen()