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:

\b((?-i:L)ondon)\steam\sis\sgoing\s\bback\s(?:to|2)\s\1\b

I was very proud at what they had learned over the past couple of weeks.