Here is the example he gave me:
I am looking for a way to detect recursion loops in a specified AD Group. Take this example of groups and members. I started with Group1, and found Group2, with group member Group2. Group2 has a group member Group3. Enumerating Group3 finds Group1, and loop!
He also said: Some groups are nested many levels down, and a single top level group can have more than one recursive loop. The script should be able to not only identify Group1>Group3>Group1, but also Group1>Group8>Group5>Group15>Group1.
This is a good use case for recursion.