SET TERM ^ ;

CREATE OR ALTER PACKAGE PKG_TEST
AS
BEGIN
  PROCEDURE test RETURNS (out_prm VARCHAR(16));
END^

RECREATE PACKAGE BODY PKG_TEST
AS
BEGIN
  PROCEDURE test
  RETURNS (out_prm VARCHAR(16))
  AS
  BEGIN
    out_prm = 'ABC';
  END
END^

SET TERM ; ^

EXECUTE IBEBLOCK
AS
BEGIN
  EXECUTE PROCEDURE pkg_test.test RETURNING_VALUES (:res);
END