function mod($data, $op = null) {
		if (!($this->data instanceof Expr)) {
			$this->data = new Expr($this->name);
		}
		
		if ($data instanceof Expr) {
			$this->data->add($data);
		} elseif (!isset($op) && is_numeric($data)) {
			$this->data->add(new Expr("+ $data"));
		} else {
			$this->data->add(new Expr("%s %s", isset($op) ? $op : "||", $data));
		}
		
		return $this;
	}