-more messages; and, the \*(lqbegin\*(rq directive (#begin), which is
-used to create a multipart content.
+more messages; the \*(lqbegin\*(rq directive (#begin), which is
+used to create a multipart content; and the \*(lqon/off/pop\*(rq
+directives (#on, #off, #pop) which control whether any other
+directives are honored at all.
+.PP
+The
+.B \-directives
+switch allows control over whether mhbuild will honor any of the
+\*(lq#\*(rq-directives. This can also be affected with the #on or
+#off directives, and #pop, which restores the state of processing to
+that preceding the most recent #on or #off. (The #on, #off, and #pop
+directives are always honored, of course.) This allows inclusion of
+plain text which looks like mhbuild directives, without causing
+errors:
+.PP
+.RS 5
+.nf
+#off
+#include <stdio.h>
+
+printf("Hello, World!);
+#pop
+.fi
+.RE
+.PP
+Currently the stack depth for the #on/off/pop directives is 32.