use macro for /usr/local/plan9
diff --git a/man/man3/draw.3 b/man/man3/draw.3
index be5e6c6..39f2b81 100644
--- a/man/man3/draw.3
+++ b/man/man3/draw.3
@@ -805,7 +805,7 @@
 .I on
 is non-zero.
 .SH SOURCE
-.B /usr/local/plan9/src/libdraw
+.B \*9/src/libdraw
 .SH SEE ALSO
 .IR graphics (3),
 .IR stringsize (3),