I checked your snippet with same results like you. So I'm now more unillumined as before my post. I played a little bit with your code and find that there must be a local $@ in the code hierarchy. I'm relative sure that is not explicit set inside of my code. Maybe in a module I use but I do not understand why it is localized. Can someone please give me a hint how to find the place where $@ is maybe localized. Thanks in advance.