I am learning regex and I found the following pattern:

```
q(?=u)i

```

If I try to math `quit`, it fails, because q matches q, u matches u (so the lookahead is valid), but then the regex backtracks in the word `quit` and the character u is compared again, this time with i. The match fails.

I don't see any word matching this pattern. Is there any case? Or is this structure (pattern - lookahead - rest of pattern) useful?