C:\_32\pscrpt>type t1.txt
Hello

C:\_32\pscrpt>type t2.txt
World

C:\_32\pscrpt>perl -wle "$ret = system 'diff', '-u', 't1.txt', 't2.txt';print $ret; print $?"
--- t1.txt      Mon Jun  6 22:42:29 2011
+++ t2.txt      Mon Jun  6 22:42:42 2011
@@ -1 +1 @@
-Hello
+World
256
256