There's a tutorial in the Community Guide part 2.
The part it doesn't explain, though is how to modify the *.fpe file in the first place.
The best way i found was to search through the various character *.fpe files until you find one with all the limbs defined. I think the AI.fpe has it.
Copy all the lines associated to limb definition and pasted them into the character you want to have limb detection.
Then follow the guide about finding out which limb is the head, arm, etc.
And then you should be ready for limb detection within your game.
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