As for slowing things down, does the line ending ever change? Figure it out once, and remember it. You could even make that part of installation.

Here is another idea. You can have a known file containing the line ending candidate and just read it. See which one was transformed into a simple "\n".

So, open (without binmode) lineend_mac and read it; ditto for lineend_pc and see which was a "\n". Neither really contained just a "\n".

—John