+.PP
+The
+.B \-debug
+switch causes pick to output a representation of the search pattern.
+.SS "Output when no messages are matched"
+If
+.B pick
+is used in a backquoted operation, such as
+.PP
+.RS 5
+scan\0`pick\0\-from\0jones`
+.RE
+.PP
+and
+.B pick
+selects no messages (e.g., no messages are from \*(lqjones\*(rq),
+then the shell will still run the outer command (e.g.,
+.BR scan ).
+Since no messages were matched,
+.B pick
+produced no output, and the argument given to the outer command as a
+result of backquoting
+.B pick
+is empty. In the case of
+.B nmh
+programs, the outer command now acts as if the default `msg' or `msgs'
+should be used (e.g., \*(lqall\*(rq in the case of
+.BR scan ).
+To prevent this unexpected behavior, if
+.B \-list
+was given, and if its standard output is not a tty, then
+.B pick
+outputs the illegal message number \*(lq0\*(rq when it fails.
+This lets the outer command fail gracefully as well.