# [Perl 5] `-pl`, 31 bytes <!-- language-all: lang-perl --> $k{$_}++}{$_=!grep$_-2,values%k [Try it online!][TIO-lrzccuw5] [Perl 5]: https://www.perl.org/ [TIO-lrzccuw5]: https://tio.run/##K0gtyjH9/18lu1olvlZbuxZI2SqmF6UWqMTrGumUJeaUpharZv//b8hlxGXMBSFNuUz/5ReUZObnFf/X9TXVMzA0@K9bkAMA "Perl 5 – Try It Online"