CASE Statement - Order of expression processing

I observed the following behaviour (I tested the following statements in 9.0.4, 9.0.5 and 9.3beta1):

$ psql template1
template1=# SELECT CASE WHEN 0=0 THEN 0 ELSE 1/0 END;
 case
------
    0
(1 row)

template1=# SELECT CASE WHEN 1=0 THEN 0 ELSE 1/0 END;
ERROR:  division by zero

In this case the CASE behaves as expected.

But in the following expression:

template1=# SELECT CASE WHEN (SELECT 0)=0 THEN 0 ELSE 1/0 END;
ERROR:  division by zero

(Just to be sure, a "SELECT (SELECT 0)=0;" returns true)

It seems that when the "CASE WHEN expression" is a query, the evaluation order changes.