$apm install regex-railroad-diagram

• linter がバグる場合は，linterをdisableする．
• 正規表現をグラフィカルな路線図で表してくれる．

e.g.

^(?:(?:(?:0?[13578]|1[02])(\/|-|.)31)\1|(?:(?:0?[13-9]|1[0-2])(\/|-|.)(?:29|30)\2))(?:(?:1[6-9]|[2-9]\d)?\d{2})$|^(?:0?2(\/|-|.)29\3(?:(?:(?:1[6-9]|[2-9]\d)?(?:0[48]|[2468][048]|[13579][26])|(?:(?:16|[2468][048]|[3579][26])00))))$|^(?:(?:0?[1-9])|(?:1[0-2]))(\/|-|.)(?:0?[1-9]|1\d|2[0-8])\4(?:(?:1[6-9]|[2-9]\d)?\d{2})$
https://stackoverflow.com/questions/800813/what-is-the-most-difficult-challenging-regular-expression-you-have-ever-written

References:
https://atom.io/packages/regex-railroad-diagram