Well... I could reply a ´thank you´ to all given answers but instead, I do it all at once. Combining all the answers and the perlsec manpage, I now also understand what tainting is and why it (is|may be) use ful.
Yes, thank you for not replying to everyone. It is very annoying. Next time, please consider using the Chatterbox for this or Super Search. This question has been asked at least 100 billion times now.