Yep, Applescript. Quick Google search turns up this: http://smoove-operator.blogspot.com/2011/05/gtd-intake-autom...

Worth mentioning that OmniFocus has a built-in tool for this (humorously called the "Clip-o-Tron 3000")

I use the auto-fill plugin that Cultured ships with the app. I didn't have to use any Applescript.