use macro for /usr/local/plan9
diff --git a/man/man1/bc.1 b/man/man1/bc.1
index 9bb0f08..bd180a5 100644
--- a/man/man1/bc.1
+++ b/man/man1/bc.1
@@ -270,7 +270,7 @@
 .B /sys/lib/bclib
 mathematical library
 .SH SOURCE
-.B /usr/local/plan9/src/cmd/bc.y
+.B \*9/src/cmd/bc.y
 .SH "SEE ALSO"
 .IR dc (1), 
 .IR hoc (1)