(suggested by Michael G Schwern)
p4raw-id: //depot/perl@29816
C<use feature 'state'> tells the compiler to enable C<state>
variables from here to the end of the enclosing BLOCK.
+See L<perlsub/"Persistent Private Variables"> for details.
+
=head1 FEATURE BUNDLES
It's possible to load a whole slew of features in one go, using