I have a need to lay out source blocks side by side, in order to present
before and after changes to the source. If I could embed a block in a
table, that would do it.

Is there another obvious way that I'm missing?

Hilight etc is important, but also actually compiling the code to maintain
correctness.

https://isocpp.org/files/papers/D1988R1.html

Has an example at the top. That's done with pandoc markdown with a bunch of
post processing. I'd like to go back to org.