use macro for /usr/local/plan9
diff --git a/man/man1/grap.1 b/man/man1/grap.1
index 8fbfaaa..d9dae3f 100644
--- a/man/man1/grap.1
+++ b/man/man1/grap.1
@@ -404,7 +404,7 @@
 .B /sys/lib/grap.defines
 definitions of standard plotting characters, e.g., bullet
 .SH SOURCE
-.B /usr/local/plan9/src/cmd/grap
+.B \*9/src/cmd/grap
 .SH "SEE ALSO"
 .IR pic (1), 
 .IR troff (1)