My apologies, if I didn't get my point across. I did not want a solution for my program, which is why I intentionally posted a minimal proof of concept.

The original snippet is working and demonstrates what problem I have, that reading a config file, which is no problem normally, generates a warning when forced to execute in BEGIN. Input data (apart from a file that is recognized as a config file by Config::Std), output data does not exist.

Also I do not want to fix anything, I want to understand why a 'once' warning is triggered in this special case, where in my intuition it should not be triggered.