You could of course create a cgi based login system in a popup but I don't believe that is what you asking for.

As far as I am aware there is no way to emulate the apache auth functionality. It seems like a waste of effort to duplicate functionality when you can just use it as it is. If you want to manage the users and passwords from perl you can use Apache::Htpasswd to manipulate the .htpasswd file.

I want to control the behaviour (enabling/disabling) of the authentication based on dynamic variables in the Perl code, that's why I really can't use it as it is.
I guess I can use mod_perl in some way, but the environment for this specific task is very strict - I really can't install mod_perl in the target environment.

I think you really just need to create a cookie based login session system. If you have reasons for not wanting to store users in a database then you can still use a .htpasswd file for storing users. I think App::Authentication::Htpasswd should allow you to do that.

Catalyst/plack/mojolicious/dancer/dancer2... do it, see Catalyst::Authentication::, plack auth, Mojolicious::Plugin::DigestAuth

So write your application to be compatible with PSGI (ie Plack )

Or write your application as an actual plack/mojo/catalyst application

Use their Digest Access Authentication plugins and you're done

Then you can deploy to any server, as mod_perl/cgi/fcgi.... plackup