use macro for /usr/local/plan9
diff --git a/man/man3/keyboard.3 b/man/man3/keyboard.3
index f341e50..4641b86 100644
--- a/man/man3/keyboard.3
+++ b/man/man3/keyboard.3
@@ -84,7 +84,7 @@
 structure.
 .PP
 .SH SOURCE
-.B /usr/local/plan9/src/libdraw
+.B \*9/src/libdraw
 .SH SEE ALSO
 .IR graphics (3),
 .IR draw (3),