OK, there might have been a misunderstanding here. And that was my fault, because I didn't specify my requirements and background in detail. I will give some additional details, but I will have to limit it to a high-level overview:

The plan is to use a Perl-based test harness to support the QA and DEV groups of a large company with automated tests. There's something like this in place already, but it has limitations, which is why we're redesigning parts of it. In our environment we have a server running our product and multiple clients accessing this server. This is why we're already using Expect and will most likely also do so in the future. The server itself is not written in Perl, so we're not trying to test Perl code, but the different features of the server instead. This will include functional, error recovery, stress and other tests.

I don't want to go into all the details, because this will become too much to post here. Which doesn't mean that we're not looking into those details ourselves. Here I just wanted to see if others know about CPAN modules I should start looking at, which I might have missed so far. There were a few good tips already, but more are certainly appreciated.