There are always cases where you can't avoid whitebox testing.

I'm limiting the inserted test code to the absolute minimum, any print, dump or log would have the same damage.

( But now I understand the point of Test::Inline better to generate test code out of embedded POD)

I wished I could go into a deep analysis of the code base and help sketching some architectural advice which is followed by all programmers here.

Unfortunately that's not how it works and not what I was hired for.

It would involve weeks of discussions and arguments with management and colleagues, of whom many are only self-trained part-time programmers.

At the same time I have to deliver the projects I was commissioned with.

We are already glad to have introduced testing and real version control for the time being.