Why is the output surrounded by (brackets)?

freshports.org=# select all_depends_lib_text('sysutils/bacula-server');
              all_depends_lib_text
-------------------------------------------------
 (pq.3:/usr/ports/databases/postgresql74-client)
(1 row)

freshports.org=#


CREATE OR REPLACE FUNCTION all_depends_lib_text(text) RETURNS text AS
$$
DECLARE
    p_category_slash_port   ALIAS for $1;
    l_depends               TEXT;

    r                       RECORD;

BEGIN
    l_depends := '';
    FOR r IN SELECT depends_lib FROM ports_all WHERE id = 13990 LOOP
        l_depends := l_depends || ' ' || r.depends_lib;
    END LOOP;

    RETURN r;
END
$$
LANGUAGE plpgsql;


freshports.org=# SELECT depends_lib FROM ports_all WHERE id = 13990;
                  depends_lib
-----------------------------------------------
 pq.3:/usr/ports/databases/postgresql74-client
(1 row)

freshports.org=#