Opensource.com - https://opensource.com/article/18/3/easy-data-validation-regexpcommon
Building regular expressions in Perl can be a little bit tricky, particularly for the newcomer. It’s a powerful technique, but even experienced Perl developers can sometimes find themselves checking the documentation to make sure they’ve got it right.
Another common issue with regular expressions lies in the common expressions we use all the time; it seems like we’re forever re-inventing the wheel! But, for this problem at least, there is a useful answer.