use macro for /usr/local/plan9

man/man1/sam.1

@@ -865,27 +865,27 @@ The answer
 .L y
 causes writing; anything else skips the file.
 .SH FILES
-.TF /usr/local/plan9/src/cmd/samterm
+.TF \*9/src/cmd/samterm
 .TP
 .B $home/sam.save
 .TP
 .B $home/sam.err
 .TP
-.B /usr/local/plan9/bin/samsave
+.B \*9/bin/samsave
 the program called to unpack
 .BR $home/sam.save .
 .SH SOURCE
-.TF /usr/local/plan9/src/cmd/samterm
+.TF \*9/src/cmd/samterm
 .TP
-.B /usr/local/plan9/src/cmd/sam
+.B \*9/src/cmd/sam
 source for
 .I sam
 itself
 .TP
-.B /usr/local/plan9/src/cmd/samterm
+.B \*9/src/cmd/samterm
 source for the separate terminal part
 .TP
-.B /usr/local/plan9/bin/B
+.B \*9/bin/B
 .SH SEE ALSO
 .IR ed (1),
 .IR sed (1),