Regex pattern : `(?iu)(?>(?:)|(?:@\A(?>(?<varNameFirstChar>[_\p{Lu}\p{Ll}\p{Lt}\p{Lm}\p{Lo}])|(?<varNameBodyChar>(?>\g<varNameFirstChar>|[\p{Nd}]))|(?<varName>(?<!\g<varNameBodyChar>)\g<varNameFirstChar>\g<varNameBodyChar>*+))))\g<varName>` cf. [https://www.maruo.co.jp/hidesoft/2/x39719_.html?a=0#39719](https://www.maruo.co.jp/hidesoft/2/x39719_.html?a=0#39719)