COPY IN as SELECT target

Recently there was discussion about allowing a COPY statement to be a
SELECT target, returning a text array, although the syntax wasn't really
nailed down that I recall. I was thinking that we might have

COPY RETURNING ARRAY FROM ...

instead of

COPY tablename opt_column_list FROM ...

the we possibly could do things like:

SELECT t[5] as a, 3*(t[3]::numeric) as b FROM (COPY RETURNING ARRAY
FROM STDIN CSV) as t;

Thoughts?

cheers

andrew