I remember reading somewhere in this thread that \r and \n have reversed semantics on the Mac (vs. *nix, Windows).

Um, no, that statement hasn't been made on this thread.

Oh yes it has. On a Mac, "\n" is "\015" (native end-of-lines), and "\r" is the other one, "\012". The sequences you can encounter, in Ascii, are matched by /\015\012|\015|\012/.

In addition, "\015\015\012" can occur too, in HTML pages you can download from the web, because of an erroneous FTP upload from Windows to Unix, as binary — and a download as text, which adds another CR.