Make sure you have the right version of CGI::Cookie. SameSite support was added in 2016 and has been mentioned in the changelog a couple of times since.

>perl -MCGI::Cookie -E'say CGI::Cookie->new(-name=>"a",-value=>"b",-sa
+mesite=>"Lax")'
a=b; path=/; SameSite=Lax

>cpanm CGI::Cookie
CGI::Cookie is up to date. (4.54)
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