BUG #1329: Bug in IF-ELSEIF-ELSE construct

The following bug has been logged online:

Bug reference:      1329
Logged by:          Rico Wind

Email address:      rw@rico-wind.dk

PostgreSQL version: 8.0 Beta

Operating system:   Windows XP, SP2

Description:        Bug in IF-ELSEIF-ELSE construct

Details:

Beta 1.
The following always returns 4:

IF from_date_param=period_begin AND until_date_param=period_end
THEN
    return 1;
ELSEIF from_date_param=period_begin
THEN
    return 2;
ELSEIF until_date_param=period_end
THEN
    return 3;
ELSE
    return 4;
END IF;

Whereas the following returns the right answer(not 4 each time). They should
be the same.
IF from_date_param=period_begin AND until_date_param=period_end
THEN
    return 1;
ELSE
    IF from_date_param = period_begin
    THEN
        return 2;
    END IF;

    IF until_date_param=period_end
    THEN
        return 3;
    END IF;
END IF;
RETURN 4;