I currently develop Perl code exclusively on Windows. However, some of my clients run my code on Unix and it almost always works even though I don't test it. My code does not create any filename that would not be a proper Perl variable name. That is more restrictive than it needs to be. However, if I create file "abc_123" (no spaces in the file name) from "abc 123" that does not seem to cause any significant issues for Windows users - they get it.