Thank you for your post.
I am able to replicate the problem on both Mac and Windows computers running FileMaker Pro 10 and 11.
I have forwarded your post along with my findings to our Development and Software Quality Assurance (Testing) departments for review and confirmation. When I receive an update, I will let you know.
Here is some information I received from Testing and Development...
"The script result will live for the life of the script or until it is explicitly overwritten by another Exit Script call. The second Exit Script from the subscript does not overwrite the return value so the value set from the first subscript persists. The documentation for Get (ScriptResult) is inaccurate. If the script result already has a value then the user needs to explicitly clear the value if they need it to be cleared."
The information has been sent to the Manager of our product documentation to be updated in a future release.