I got to understand better the whole concept of having a bytecode format for executables, with JIT/AOT deployment options when I started delving into the old mainframe world.
I used to do AS/400 backups, but never coded for it. So it was quite interesting to discover the all TIMI concepts.
Also other similar environments like the Burroughs B5000.
The old is new again. :)
I wonder why this isn't bigger in the FOSS world...maybe because the source and toolchain are already available...I don't know, it might be a neat idea to have an IR userland that compiles on install.