Yep, it's debugger's output prefix.
That problem seems like either :
1) You are running a .debug application outside of a debugging environment (like the IDE) - which, if something causes the app to break (like an exception), expects there to be an actual DEBUGGER ready to catch it and perhaps show you the line that has crashed.
2) You are running the application inside the IDE, but for some reason the Pipe/stream between the application and the debugger is lost, causing it to dump it to the console.
1 is most likely. I often get it when running a .debug app in gdb.
HTH
:o)
|