Describe SEL and JOIN, with a couple examples.
Simple closure explanation.
Include longer instruction names.
Draft non-rec function instruction descriptions.
Extra section in optimizing the instruction set.
Start on reduce/map/filter in SECD.
Built-in instruction MOD.
Filter example in SECD instructions.
Reverse map/filter return vals for correct order.
Use extended instruction set.

secd-reduce is tail recursive, and use TEST instead of SEL for
in-function branching statements.
Recursive "Hello world" example.
Draft description of "Hello, world" example.
Outline of reduce/map/filter description.