Comment 1984 added to page plpgsql.html of version 7.4

Author: James Nakasone Wong <janaka_tech@bluebottle.com>
----
=====================
CREATE FUNCTION somefunc() RETURNS integer AS '
DECLARE
    quantity integer := 30;
BEGIN
    RAISE NOTICE ''Quantity here is %'', quantity;  -- Quantity here is 30
    quantity := 50;
    --
    -- Create a subblock
    --
    DECLARE
        quantity integer := 80;
    BEGIN
        RAISE NOTICE ''Quantity here is %'', quantity;  -- Quantity here is 80
    END;

    RAISE NOTICE ''Quantity here is %'', quantity;  -- Quantity here is 50

    RETURN quantity;
END;
' LANGUAGE plpgsql;

==============================
I 've  saved above text in f2.sql
then when I upload this file (f2.sql) an error appeared?  can anybody advice what shall I need to do from there ?

============================
test=# \i f2.sql
psql:f2.sql:20: ERROR:  language "plpgsql" does not exist
HINT:  You need to use "createlang" to load the language into the database.
test=#
----
Manual page: http://wwwmaster.postgresql.org/docs/7.4/interactive/plpgsql.html
Reject:      http://wwwmaster.postgresql.org/admin/comments.php?action=reject&id=1984
Edit:        http://wwwmaster.postgresql.org/admin/comment-edit.php?id=1984
Delete:      http://wwwmaster.postgresql.org/admin/comments.php?action=delete&id=1984