prepared query plan did not update - Mailing list pgsql-sql

Good morning,

I tried to use prepared query plan to update columns, but it did not 
update at all.

PREPARE pname(varchar) AS
UPDATE t1
SET    col1 = false
WHERE  col1 AND       col2 = '$1' ;
EXECUTE pname( 'value' )



Could someone tell me where I did wrong please?

Thanks alot!