Question

Problem is easier to be seen in code then described I got following regex

 (?<=First(Second)?)\w{5}

and following sample data

FirstSecondText1
FirstText2

I only want matches Text1 & Text2 , I get 3 though, Secon is added, and I don’t want that.
Played around, cant seem to get it to work.

Answer 1

You need an additional negative lookahead:

(?<=First(Second)?)(?!Second)\w{5}

If you want to avoid using Second twice, you could do it without lookaround and take the result of the first capturing group:

First(?:Second)?(\w{5})