That doesn't work. `(?:"Tarzan".*?)*\KTarzan` should behave identically without `\K`, and it will match `"Tarzan" "Tarzan"` because the ungreedy quantifier ? still allows backtracking (it just changes the search order). You want the possessive quantifier + instead; `not_this|(but_this)` is equivalent because regexp engines will not look back into once matched string.

Interesting. I took the \K solution right from the article without trying it.

Now that I try it, it indeed does not work.

Maybe the author reads this and can look at it.