## [Perl 5], 43 bytes

__42 bytes code + 1 for `-p`.__

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    s//K Ks
    K unKs/;s/K/known/g;$_.=s/^/un/gmr

[Try it online!][TIO-j8u965ao]

[Perl 5]: https://www.perl.org/
[TIO-j8u965ao]: https://tio.run/##K0gtyjH9/79YX99bwbuYy1uhNM@7WN@6WN9bPzsvvzxPP91aJV7Ptlg/Tr8UyMkt@v@f619@QUlmfl7xf90CAA "Perl 5 – Try It Online"