Replace the n-tuple in B with the n + 1-tuple (B:Result).
Result B.
For each of the variables named in B, proceeding from
left-to-right, perform the following operations:
Place the next variable in B into A.
If the variable in A is a global variable, do action 3 of
glvn.
Place the value in Result in the variable named in A. If the
variable named in A has the form of a setpiece, the details of
this action are described in Section 3.6.15 of Part I.
B.