very interesting question! and I wait for other's answer. Not a web expert here at all, so just some sparse considerations

What suggested above, ShinyCMS, seems nice but it seems also they switched to Ruby in 2021. Infact the actual repository just mention a previous version written in Perl with Catalyst. Not everyone fears old unmaintained things here around though ;)

I'd fear a no more maintained CMS.

In CPAN I found Slovo: a simple to install and extensible Mojolicious CMS with nice core features and it was updated in 2023. I see also very well known Perl hackers among contributors. Mojolicious usage sounds as a plus for me.

About authentication: I remember a (Perl?) video strongly suggesting to externalize the authentication wherever it is possible. It is so crucial and risky that delegate it outside (login with: BigGlasses, VisageTome.. ) sounds wise (in this case forget my signature).

The Perl's panorama on CMS seems a Pompei view and if this is true, also a bit risible.

I wait for other's replies and if you find something interesting please share it with us.

L*