On chapter 34, you teach the how to not pollute the registers and recover the "@ register.
This is correct, but it doesn't work if clipboard is set to unnamed. In that case "+ and "* registers are used instead, so they should also be recovered.
Thanks a lot by the way, I learn a lot from the online version and will definitely buy it as soon as I finish reading it.
If you start accepting PRs again let me know and I'll happily create one.