Thanks for your investigations into this.

While I don't really like these sorts of loose ends and things I don't fully understand, at the end of the day it's a very minor issue. I can easily change the line endings with a short one-liner: there's quite a swag of legacy code like this that I'll need to deal with in the not too distant future. And, if I don't change them, the warning is harmless as far as I can tell: there's no indications of side-effects or other problems waiting in the wings.

Perhaps bingos will have an answer; although, I don't think he visits very often. I've encountered his name on many occasions in CPAN testers reports and the acknowledgements section of deltas; however, checking his Writeups, his last post was over seven years ago in 2015.