in the latter case, it is usually counter-productive to declare $a and
$b as lexicals.
-In either case, the subroutine may not be recursive. The values to be
-compared are always passed by reference and should not be modified.
+The values to be compared are always passed by reference and should not
+be modified.
You also cannot exit out of the sort block or subroutine using any of the
loop control operators described in L<perlsyn> or with C<goto>.