use macro for /usr/local/plan9
diff --git a/man/man3/sleep.3 b/man/man3/sleep.3
index da2e695..7df6c33 100644
--- a/man/man3/sleep.3
+++ b/man/man3/sleep.3
@@ -37,7 +37,7 @@
 The return value is the amount of time previously remaining in
 the alarm clock.
 .SH SOURCE
-.B /usr/local/plan9/src/lib9/sleep.c
+.B \*9/src/lib9/sleep.c
 .SH SEE ALSO
 .IR intro (3)
 .SH DIAGNOSTICS