He is saying you are then different, and not the same. Changes have been made. Perfection is perfection, and if you are now something different, you cant still be perfect.
And with my example, more related to christianity, if god is perfect, and he is only able to do things consistent with his natue (one aspect of which is perfection), then he is not able to create imperfect things. We see imperfections of his creation in everyday life, and in the bible. Therefore he is not perfect.