Man pages matching name http::server::simple::authen in section 3pm:

HTTP::Server::Simple::Authen.3pm.en	debian 10 / libhttp-server-simple-authen-perl
HTTP::Server::Simple::Authen.3pm.en	debian 11 / libhttp-server-simple-authen-perl
HTTP::Server::Simple::Authen.3pm.en	debian 12 / libhttp-server-simple-authen-perl