use macro for /usr/local/plan9
diff --git a/man/man1/doctype.1 b/man/man1/doctype.1
index cb339ae..02a3601 100644
--- a/man/man1/doctype.1
+++ b/man/man1/doctype.1
@@ -43,7 +43,7 @@
 .BR chapter.1 ,
 \&...
 .SH SOURCE
-.B /usr/local/plan9/bin/doctype
+.B \*9/bin/doctype
 .SH SEE ALSO
 .IR troff (1), 
 .IR eqn (1),