One question: is there any way to have it reread the "notes" file periodically without having to stop/start the script?

Sure. There are two changes needed: replace the "while (<>) ..." with more robust file handling, and add some code to re-read the file(s) provided when they change.

Not huge changes, but I guess I didn't envision this being a particularly long-lived script. I was thinking more start it up, work for a few hours, shut it down.