|laziness, impatience, and hubris|
that was a very valuable hint (sorry, can't do more than one ++). I really assumed that I use the newset version. Sometimes I hate myself for my (not proved) assumptions.
So, fact is, I didn't use the newest version. The output above is based on version 0.72 of Net::DNS.
So, for the protocol I installed the newest version 0.74 and let the whole thing run again. This looks much better now even I can't explain where the fixed costs in terms of base leaks come from. The output now is:
That means I do have a kind of usage penalty, but it seems that the consumption raises not with the count of lookups. I'll see when I lookup different domains.
Once again: Thank you for pointing out the obvious, which I haven't done: Look at the newest version and have a look at the bug history. Be sure, I will make atonement for that as it's expected from a monk. ;-)