1. Relate each of the above steps (a) to (d) and (ca) to (ci) above to the five types of implicit uses of the stack.
2. Step through the examples with different input numbers, e.g. 4 and 5 instead of 3 and 5, keeping track of which intermediate numbers are created.
3. Do the same with the procedure volume, defined in Chapter 1. (It is easier than perim.)
4. If you have found the explanations so far confusing, you may find it helpful to work through the online Poplog file TEACH STACK, which explains these points in more detail, with more examples. TEACH DEFINE may also help.