indirect references to static function variables

Hi again,
the ZEND_CHANGES file states:
[...]

• Static function variables.

Statics are now treated at compile-time which allows developers
to assign variables to statics by reference. This change also
greatly improves their performance but means that indirect
references to statics will not work anymore.
[..]

The only thing close to "indirect references" I could come up
with, was this:
<?php
function foo()
{
static $a = 0;
$a_name = "a";

echo $$a_name;
echo $a;
$a++;
}

foo();
foo();
?>

Which works as expected in both PHP 4 and 5.

So what exactly doesn't work anymore? Or what is meant by
"indirect references"?

Best regards,
Jan