code: public static boolean isDebugMode() {
          if (debugMode==null) {
              setDebugMode( Boolean.valueOf(System.getProperty(DEBUG_LAUNCH_KEY)) );
          }
          return debugMode;
      }
docs: Returns current debug mode.<br/>
  Holds lazy initialized internal reference to improve performance.<br/>
  Therefore you can't change System property "mvel.debugger" after isDebugMode is called at least once.<br/>
  <br/>
  To update debug mode at runtime use {@link MVELDebugHandler#setDebugMode(boolean)}<br/>
  @return <code>true</code> if debug mode is enabled.