https://www.php-fig.org/psr/psr-16/ Key - A string of at least one character that uniquely identifies a cached item. Implementing libraries MUST support keys consisting of the characters A-Z, a-z, 0-9, _, and . in any order in UTF-8 encoding and a length of up to 64 characters. Implementing lib...

This matches shell shebangs (bash / sh). It could be used e.g. to find shell files (via grep -m1 -EIrl 'exp').

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Regex to decode levelnumber, starecase and door in a single string