use macro for /usr/local/plan9
diff --git a/man/man1/fmt.1 b/man/man1/fmt.1
index 997b71b..7bdfe25 100644
--- a/man/man1/fmt.1
+++ b/man/man1/fmt.1
@@ -81,9 +81,9 @@
 as the base URL for the document when displaying anchors; sets
 .BI -a .
 .SH SOURCE
-.B /usr/local/plan9/src/cmd/fmt.c
+.B \*9/src/cmd/fmt.c
 .PP
-.B /usr/local/plan9/src/cmd/htmlfmt
+.B \*9/src/cmd/htmlfmt
 .SH BUGS
 .I Htmlfmt
 makes no attempt to render the two-dimensional geometry of tables;