documentation on the caret

From: Marco Scoffier (marco_at_metm.org)
Date: 12/20/04 

Date: Mon, 20 Dec 2004 00:35:09 -0500

can someone point me to somewhere online which describes how the caret
works in :

  v(e,1,X^go(X)) --> [went].

I found this usage here:
  http://courses.essex.ac.uk/lg/LG619/mt/index_0.html#32

It looks like I am getting extra "slots" without changing the "footprint"
of my rule and this is what I want (I am not using the correct words I
know).

Unfortunately google-ing for the '^' or 'prolog caret' does not work very
well.

Thank you for your help, 

-- 
Marco