public function path(array $values, $operator)
    {
        if (!in_array($operator, array('=', '!='))) {
            return $this->translation->text('Unsupported operator');
        }

        foreach ($values as $pattern) {
            if (!gplcart_string_is_regexp($pattern)) {
                return $this->translation->text('@field has invalid value', array(
                    '@field' => $this->translation->text('Condition')));
            }
        }

        return true;
    }