VARIABLE

Variable definitions
TTITLE/BTITLE

Antother one
There is a deprecated syntax that should be tackled, that is pending
BREAK, COMPUTE, REPHEADER, REPFOOTER

Formatting commands, tested against "Formatting SQL*Plus Reports"
SQL*Plus documentation
Fixes of other definitions as a result of applying to random files
RUN - /

Consider that anything after them is ignored
ATTRIBUTE, COPY, DISCONNECT, EXECUTE, EXIT...

... WHENEVER, ACCEPT (partial)

Getting there, this is getting tricky even if reusing, due to minor
differences in syntax and major differences on how sqlplus parses
commands

I'm learning stuff, though, which makes this somehow worthwhile