Hmm, my first reaction was that it seems to me that Perl is able to deal with DOS end-of-lines (^M) under *nix without any problem within the script itself (and I think the other way around too). Not that I have ascertained it by making a decisive test on it, but after having developed programs under Windows and run them under Unix for so many years, it is almost doubtless that I would have encountered the problem if Perl wasn't able to deal with that, and I am almost sure I have never met it.

Having said that, other non-printing characters is definitely a possibility, I ran into this type of problem just a couple of days ago under VMS: for some reason, my Windows editor added some presumably utf-8 character at the very beginning of my program, which refused to even compile.

And, thinking back to my initial reaction in my first sentence above, it is absolutely true that if the shebang line is faulty, well, it is not interpreted by Perl but by the shell. And the shell is not as clever as Perl. But then, maybe I should have met the problem with DOS formated Perl script? Well, probably not, because I actually almost never really use the shebang line, my Unix shell scripts running Perl programs almost always launch the Perl program with a command such as perl my_script.pl (this way I don't run into RWE problems if I forgot to change privileges). And the same when I run a Perl program directly from the shell prompt. So that, in the end, your hypothesis might very well be right.

Well, all this to say that I initially thought you were probably wrong, and that, after a second thought, I think you might be right.