http://120.105.184.250/cswang/thit/Linux/RegularExpression.htm
https://atedev.wordpress.com/2007/11/23/%E6%AD%A3%E8%A6%8F%E8%A1%A8%E7%A4%BA%E5%BC%8F-regular-expression/
https://regexone.com/
https://regexone.com/references/python
這個網頁可以直接測試「正規表示法」
https://regex101.com/