protected function getRegex()
    {

        if( !self::$regexDefault ) {
            self::$regexDefault = implode(
                '|',
                array_map(
                    function($value){
                        return "(?<=[a-z0-9]){$value}(?=[A-Z])";
                    },
                    array_flip( self::$operations )
                )
            );
            self::$regexDefault = "/".self::$regexDefault."/";
        }

        return self::$regexDefault;

    }