Article writer here.

A lot of our CI/CD is designed around mod_perl, and in-place updates. We run NewRelic configured to monitor Apache, which stops us from having to roll our own NewRelic connection through a CPAN module that we'd have to audit. In general for our needs, I actually believe mod_perl is superior to (F)CGI or a PSGI server reverse proxy.

Mod_perl was really tied into Apache. You could basically script the web server internals at a completely different level then (f)CGI and friends. In contrast, (f)CGI emphasizes a clean interface between different (os) processes. Both has its reasons to exist.