ok how this perk works is if you hold down ... you will fall to the ground like a rag doll (much like feigning death) if a enemy is shooting you and you do this they will think you're dead and walk off. talk to other enemies etc high level enemy may not fall for this

There are already several topics about perks, http://www.gamesas.com/index.php?/topic/1095509-new-vegas-perks/ so no need for another.