That warning has never happened to me. Perhaps it's a security feature on your system. The $1 is supposed to be a substitution parameter so that the script name is given to /usr/bin/perl.

I remember that I entered ".ppl" in the box, but that later it reported just "ppl", so that is ok.

You might try to run something simple to start with, like printing a line to a file in /tmp, to see if you are really getting perl to execute at all.