Konami is adding a few control options to the Vita version of Metal Gear Solid HD Collection. Hideo Kojima tweeted you can slit an enemy’s throat with your knife by flicking the rear touchpad. Use a pinch out motion on the rear touchpad while in first person view and you can stretch your character.
Kojima mentioned these controls while recording new lines for Major Zero in Japan. In Japan, Metal Gear Solid HD Collection is called Metal Gear Solid HD Edition since it only includes Metal Gear Solid 2 and Metal Gear Solid 3.