v the match any statements are like: match `hallo`, `hallobob`, `hallobier`

Negative lookahead: `hallo(?!blaat)`: match any hallo but not in halloblaat
Positive lookahead: `hallo(?=blaat)`: only match hallo in halloblaat

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Negative lookbehind: `(?<!hallo)blaat` : match any blaat except in halloblaat
Positive lookbehind: `(?<=hallo)blaat` : only match blaat in halloblaat
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