Hello Tom,
> Please look at changing \into to be a SQL-command-ending backslash
> command as we previously discussed.
Hmmm.
I do want storing results & compound command ending to be orthogonal.
In order to keep this feature, I think that I can move the 
"into/ginto/gset/..." at the end of the command. For the compound command 
list to necessarily end, I can probably do some reassembly as a post phase 
on Commands in pgbench so that the impact on the lexer is much reduced, in 
particular without undue "hackery" as you put it.
-- 
Fabien.