Annoying messages when copy sql code to psql terminal

Whenever I use copy-paste to run code in a terminal window that is
running psql, and the code contains a row like

IF FOUND THEN

then I get the words

ABORT        CHECKPOINT   COMMIT       DECLARE      EXECUTE
INSERT       MOVE         REINDEX      ROLLBACK     SHOW
UPDATE
ALTER        CLOSE        COPY         DELETE FROM  EXPLAIN
LISTEN       NOTIFY       RELEASE      SAVEPOINT    START
VACUUM
ANALYZE      CLUSTER      CREATE       DROP         FETCH        LOAD
       PREPARE      RESET        SELECT       TRUNCATE
BEGIN        COMMENT      DEALLOCATE   END          GRANT        LOCK
       REASSIGN     REVOKE       SET          UNLISTEN

That must be some kind of display of possible stuff to write after
"THEN" but it is very annoying. How to turn it of?