The remaining locale category, C<LC_MESSAGES> (possibly supplemented
by others in particular implementations) is not currently used by
-Perl--except possibly to affect the behavior of library functions called
-by extensions outside the standard Perl distribution.
+Perl--except possibly to affect the behavior of library functions
+called by extensions outside the standard Perl distribution and by the
+operating system and its utilities. Note especially that the string
+value of C<$!> and the error messages given by external utilities may
+be changed by C<LC_MESSAGES>. If you want to have portable error
+codes, use C<%!>. See L<Errno>.
=head1 SECURITY