use macro for /usr/local/plan9
diff --git a/man/man1/tee.1 b/man/man1/tee.1
index 57ca9ba..428ebbc 100644
--- a/man/man1/tee.1
+++ b/man/man1/tee.1
@@ -25,4 +25,4 @@
 .I files
 rather than rewriting them.
 .SH SOURCE
-.B /usr/local/plan9/src/cmd/tee.c
+.B \*9/src/cmd/tee.c