Loosing a head while polymorphed into a zombie, I found out that your Per is not at all affected by you being headless. Loosing your head (and still living) should definitely set your Per to 0. You should be unable to see, hear or smell without your head, but right now, well... Your Int is decreased, though, which is cool. Also the priests will see nothing strange about summoning you a new head and the gods can grant you an artificial head. 
However, this got me thinking that we could also use a Blindess status for times when you only want the player to be unable to see, but his or her perception remains unaffected - after all, you could loose your sight due to a spell or strong light, but still be able to hear and smell normally. It might also work similarly to having no light source in darkness (making the area around you dark) rather than as if you had 0 Per (when you can still see your own tile, but not even the adjacent ones).
However, this got me thinking that we could also use a Blindess status for times when you only want the player to be unable to see, but his or her perception remains unaffected - after all, you could loose your sight due to a spell or strong light, but still be able to hear and smell normally. It might also work similarly to having no light source in darkness (making the area around you dark) rather than as if you had 0 Per (when you can still see your own tile, but not even the adjacent ones).