Moxie includes conditional compilation support. Conditional compilation lets you include or exclude blocks of code when you compile. It is generally used for debugging or instrumentation where there might be large blocks of code, classes, or entire libraries that you want to use during development but then want to exclude from your release version of the application.
The documentation did not get into the release of Beta 2, so here is the PDF that describes how to use this feature:
Download file (40K, PDF)