Thank you for your advice.
My application is new and is not tied to mod_perl. The reason I am looking to develop with mod_perl, is because the application is very simple, but I want maximum performance, and minimal dependencies.
I am aware of frameworks such as Catalyst and Dancer, and I have used them in the past to create fancy web sites, but for this project I am looking to create a simple file server that serves files from disc over http. If it where any simpler, I could have done the whole thing using only Apache configuration, mod_rewrite etc, but I need a small amount of logic to serve some files on the fly that don't actually exist on disc, and divert some requests to different URLs based on the client.
Based on your advice, I took a look at Plack, and it does look feasible, lightweight, and testable. Also, I can install all the dependences via Ubuntu packages, which will simplify deployment.