Proposal: USING clause for DO statement

Hello,

I am still thinking, about using DO statement from psql console. I am
missing any parametrisation. It could not be a problem. All pl have a
support for parameters, we have a libpq function PQexecParams - so we
need only some "USING" clause. I propose following syntax (and using
from client environments)

DO $$ body $$ USING expr [ ,expr [...]];

body should to have a unnamed parameters in syntax related to any PL.
I'll use plpgsql for this moment.

so some the most simply sample should look like:

DO $$
BEGIN
RAISE NOTICE 'Hello, %', $1;
END
$$ USING 'World';

>From psql:

\set message World
DO $$BEGIN RAISE NOTICE 'Hello, %', $1; END$$ USING :message;

>From pgscript:

SET @message = 'World';
DO $$BEGIN RAISE NOTICE 'Hello, %', $1; END$$ USING @message;

>From C

values[0] = "World";
result = PQexecParams(cn, "DO $$BEGIN RAISE NOTICE 'Hello, %', $1;
END;$$ USING $1",
1,
NULL, values,
NULL, NULL,
0);

What do you thing about this proposal?

Regards
Pavel Stehule