BUG #4927: psql does "spoil" the query before sending it to server

The following bug has been logged online:

Bug reference:      4927
Logged by:          handling numeric literals with dots in psql \copy
command
Email address:      filip.rembialkowski@gmail.com
PostgreSQL version: 8.4.0
Operating system:   Linux
Description:        psql does "spoil" the query before sending it to server
Details:

8.4.0:

filip@filip=# \copy ( select 1.23::numeric as num ) to 'out.csv' with csv
header
ERROR:  syntax error at or near "."
LINE 1: COPY ( select 1 . 23::numeric as num ) TO STDOUT CSV HEADER
                        ^
\copy: ERROR:  syntax error at or near "."
LINE 1: COPY ( select 1 . 23::numeric as num ) TO STDOUT CSV HEADER
                        ^

query inside parentheses is OK.

same bug reproduced in 8.3.7