Arrgh. Face-palm.

So I look at the file with a hex editor and it's got binary data in it. But it loads up fine into my text editor, which made me assume it was just a text-based XML file.

This explains why the matching doesn't work, because the bytes I'm looking for don't actually exist as I've typed them.

Seems like binary XML files have been a default in Mac OS for quite a while - at least for the OS services.

Seems like my old code is going to be OK since it works with my own plist files which are always text. But it doesn't help me solve the main problem I started looking at today which lead me to finding the BSD grep issue.