Regular expressions are a tricky thing to pick up. The ability to write them well is a skill that takes a while to develop.
We recently hired a bunch of people in, oh, let’s say London. They were visiting here for a while learning the system and today was their last day here. We met in a conference room for a going away thingie and one of the newbies wrote the following regex on the board:
I was very proud at what they had learned over the past couple of weeks.