=< a=hoon b=hoon  The product of a, given the product of b taken as the subject.
 That is  compute b first, then compute a with all of b's information available.
 This is difficult to understand. Unpacking further:
 =< takes two children each of which is some hoon expression.
 The first child will be computed after the second child has been evaluated, and where that second child will be used as subject.
 The second child is computed first and used as the subject for computation of the first child.
