ASCII NUL characters (solution)

Suppose we have database with no tables, external tables, UDFs, ... There is only one procedure with one VARCHAR output parameter. When you execute this procedure, it will return string consisting of 5 ASCII NUL characters (binary zeroes). What is in the body of this SP ?
When assigning shorter string to longer CHAR field (or to CHAR variable, or CASTing it to CHAR), IB/FB pads it with "blanks". The character used for padding is not always the space; in fact, it depends on character set used.
The character set OCTETS is intended to store binary data, and so its padding character is - binary zero. 
CREATE PROCEDURE proc
  RETURNS (str VARCHAR(10)) AS
BEGIN
  str = CAST('' AS CHAR(5) CHARACTER SET OCTETS);
END
Ivan Prenosil (2002)