thanks for the links!
I tried a lot of things (in the links you posted), Shell says Syntax is ok, there are no fatalsToBrowser errors displayed in the browser, just the header which is printed anyway. I compiled with -cwT, anything ok.
When running the code without the fork statement, anything works fine, when running it with the fork statement anything collapsed, also Perl for itself. Windows is telling me Perl isn't working anymore and asks for sending some more information (what I denied).
I think it's an environment problem of Apache, but I don't know it for sure as I'm not that familiar with server configurations.