Persistent Example - Loading Data Only When Needed

This example demonstrates how to use persistent variables when loading data in a function. Doing things this way guarantees that the "data" value in "persistentFunction" is only loaded or changed when necessary.
This is very useful in cases such as:
- "data" is large and loaded from a network location. Network locations are not as fast as locally saved data.
- The data is large and doesn't change much from call to call of "persistentFunction"