The "presevation" variable ?

[David]

This is a relatively new version feature and is not documented except
for this:

> If variable preservation is turned on, script locals retain their values when the script is re-compiled, unless there is an error in the script. With variable preservation turned off, script locals lose their values when the script is recompiled.

There was some documentation in the readme files at one time - but I
cannot find it. Is it an engine / language feature or an IDE feature
and anyone have an example of use?