protected function _prepareRegex($word) {
        $letters = str_split($word);
        $regex = '';

        foreach ($letters as $letter) {
            $regex .= preg_quote($letter, '/') . '+';
        }

        $suffix = $this->getConfig('suffix');

        if (is_array($suffix)) {
            $suffix = implode('|', $suffix);
        }

        $regex .= '(?:' . $suffix . ')?';

        return $regex;
    }