use macro for /usr/local/plan9
diff --git a/man/man1/fortune.1 b/man/man1/fortune.1
index 371c1d6..8c9c562 100644
--- a/man/man1/fortune.1
+++ b/man/man1/fortune.1
@@ -20,4 +20,4 @@
 .B /sys/games/lib/fortunes.index
 \ \ fast lookup table, maintained automatically
 .SH SOURCE
-.B /usr/local/plan9/src/cmd/fortune.c
+.B \*9/src/cmd/fortune.c