The (?! is noncapturing as is.

However you have included a (:?, the colon depicts an (unrecognized) regexp extensionis not a metacharacter so this is treated as a regular capturing group.

Updated: clarified my statement, Sidhekin is right

In reply to Re: Non-capturing zero-width negative lookahead by varian
in thread Non-capturing zero-width negative lookahead by throop

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