CGI::Application sounds very promising, thank you for that.
I think it's time for some more revelation about what I am doing so as to avoid misunderstanding. The application actually has its own website, but it's in German, and as this site's primary language is English I thought I wouldn't bother linking. But anyway: http://www.auctober.de
Just to encourage you: I keep all code commented in English. :D

Auctober is a freeware tool for sellers on eBay Germany. I know there are many of such tools, but I think I have a few unique goals:
1) platform independence
2) no presentation layer (Webbrowser is the GUI)
3) very small (once perl is installed)

At the beginning I made the tool for myself, but then I just got a kick out of publishing it, at first for "advanced users" who knew how to install a webserver or had one. Then I included Xitami for Windows-Users, which I shipped with the application. Now I want to get rid of Xitami and ship my own 20K webserver :D

I hear your security concerns and I am aware of them. I am thinking of including at least an HTTP basic authentication in the webserver (should be easy with perl, right?). Of course I am also making sure that the requests can't access other documents besides the ones needed for the application (like /etc/passwd or so).

I am considering using DBD::SQLIte2, but the compiled version (Windows) is 1.2 MB, and that's almost as big as my whole distribution at the moment. If possible I would like to avoid that. Tie::Persistent worked really well for me and maybe I can modify it so it doesn't keep references.