use macro for /usr/local/plan9
diff --git a/man/man3/nan.3 b/man/man3/nan.3
index 69777e5..9590579 100644
--- a/man/man3/nan.3
+++ b/man/man3/nan.3
@@ -41,4 +41,4 @@
 returns true if its first argument is infinity
 with the same sign as the second argument.
 .SH SOURCE
-.B /usr/local/plan9/src/lib9/nan.c
+.B \*9/src/lib9/nan.c