perldiag: Slightly clarify diagnostic explanation

Author: khwilliamson

pod/perldiag.pod

@@ -7972,7 +7972,8 @@ and their use is legal.
 =item Use of uninitialized value%s
 
 (W uninitialized) An undefined value was used as if it were already
-defined.  It was interpreted as a "" or a 0, but maybe it was a mistake.
+defined.  It was interpreted as a "" or a 0, but it was a mistake for
+Perl to do so.
 To suppress this warning assign a defined value to your variables.
 
 To help you figure out what was undefined, perl will try to tell you