I agree with what you're saying. But in my mind, IIF() should act exactly like an If, Else, Endif. And in currently doesn't.

If this code works without error...
 Code:
$array = '0','1','2','3','4','5'
$x = 51
If $x < 6
   $test = $array[$x]
Else
   $test = $array[$x mod 10]
Endif
Then the IIF equivalent should as well, in my opinion.
 Code:
$array = '0','1','2','3','4','5'
$x = 51
$test = IIf($x < 6, $array[$x], $array[$x mod 10])