Thanks clacke, I enjoyed this a lot. Nice to be on the receiving end of the Bash info for a change ;-)

Command substitution:
It's my understanding that the newer $() form is an improvement on the older `` form largely because the substitutions can be nested. At least, when I found it years ago I was excited to be able to nest them! I assume it's nestable because the new form is easier to parse.

coproc:
This seems cool, though a little involved. I'd looked briefly but hadn't really thought about the feature. Thanks for covering it.

Since b-yeezi and I have awoken the Awk series from its hibernation recently, I'm going to cover redirection and Awk's coprocess feature as well. Episode 15 is almost ready to be recorded and uploaded.