Question: I am working on open-source project on github, and I cloned a the project by doing

`git clone git@gitlab.domain.com:project.git`

Now, All works fine, I can run the project and working on it. But this was a master branch, and now
someone has created a branch called `user_interface` and added some basic HTML, now I need to pull this `user_interface` and merge it to my local working file, so I can immediately start using these additional features from that user. But, the problem is specifying how to explicitly call call that branch `user_interface` and merge it to my local copy. 

So far, I tried only `git pull`, but it pulls the original data and merges it to my local directory, so I end up with the same copy I got the last time.

Answer: 
Apparently egrep doesn't support `{m,n}` repeat syntax:

```
$ egrep -i '((\w)\2)((\w)\4)((\w)\6)' words 
bookkeeper
bookkeeping
subbookkeeper
$ egrep -i '((\w)\2)((\w)\4)((\w)\6)((\w)\8)' words 
subbookkeeper

```

If you spell out the groups, it works.

This is on my Mac.
Your regex is correct and there is not a bug. `/usr/share/dict/words` does not contain the word "subbookkeeper".