PPWIZARD is a free preprocessor for HTML, REXX, Visual Basic or any text files.
This variable will tell you whether debug is currently on or off by returning 'Y' (its on) or 'N'.
You could use this to add comments to generated output when debug is on, etc.
You could also use the IsDebugOn() function to obtain similar information.
This is a Standard Definition which always exists (you don't need to #define it). Note that you can create your own variations or completely new ones (see the examples).