Hey, you were right! My winxp and freebsd don't care about -ws in shebang, so instead I had to "perl -ws file.pl -s=15" and it worked like charm! Thanks a lot, now I have to figure out why in the world it didn't work in shebang and how often crap like that happens, as I'm probably going to distribute my little app and I want to be sure it works...
This behaviour on Windows is easy to explain: the interpreter is invoked by looking up what program to call for file type .pl. It is then invoked with the parameters from the registry entry. Whatever you put on the shebang line (or if there is one at all) has no effect.
Why FreeBSD would behave this way also is puzzling, though..