How to get output messages to appear immediately (flushing writers)?

Modula-3 Writers are buffered. Thus, you need to issue a Wr.Flush when the output should appear immediately, for instance to prompt the user for some input. Since this can become annoying, libraries in other languages sometimes offer the option of unbuffered writes. In Modula-3, an equivalent behavior is obtained with AutoFlushWr which gets a background thread to flush a writer at a specified interval.