Gotchas

•      One is indentation, which can produce unexpected errors. You can use spaces or tabs but not both in the same script. The number of spaces or tabs in an indent must be consistent with the depth it is at

•      Another is Dead-locking. If you have a Field Extension for Field A, which tests its own value and the value of Field B, which also has a Field Extension, and tests its own value and the value of Field A, you can end up in a loop that can’t be resolved