The 'pipes' are part of the regular expression OR syntax. Using join in this way is a common trick to generate a list of alternatives: word|word|word|word. It should not be over-used because a long list can be slow: I assumed that that the number of alternatives was similar to your examples.
That you have this character in your data should not affect this directly. However, any special RE character from the data that finds itself inside the RE will have to be 'escaped' (there are several ways of doing that, including \Q, quotemeta and qr). | [reply] |