正则表达式以查找字符，但排除包含该字符的某些单词

Question

I'm trying to find all occurences of ue and replace it with ü , but not for occurences like tuell . Reason is that german words like Aktuell should not be Aktüll afterwards. I tried different approaches with lookahead and lookbehind but could not get it working. I used https://regex101.com/ to test the expression. focus is on finding via regex, replacing via PHP preg_replace is not an issue.

Answer 1

You may use a (?!ll) negative lookbehind to make sure the next 2 chars are ll right after ue :

ue(?!ll)

See the regex demo

See more details about lookarounds here .