Investigate macro-processor behavior related to defined() statement

I am running

@#if !defined(DEFINEDvar) || DEFINEDvar==0
    @#echo "Good"
@#else
    @#error "ELSE ERROR"
@#endif

and get

Macro-processing error: backtrace...
- Unknown variable DEFINEDvar
- binary operation: "macro.mod" line 1, col 29-42
- binary operation: "macro.mod" line 1, col 5-42
- @#if: "macro.mod" line 1, col 1 to line 5, col 7