ensure closed-over $resource variable is weak

[cafe@cafepc][~/workspace/Sandbox/Web-Machine-0.12]$ PLACK_SERVER=Standalone plackup -I lib examples/env-resource/app.psgi 
HTTP::Server::PSGI: Accepting connections at http://0:5000/
Unhandled type: GLOB at /home/cafe/perl5/perlbrew/perls/perl-5.16.3/lib/site_perl/5.16.3/Devel/Cycle.pm line 107.
Cycle (1):
	$A->{'web.machine.content_filters'} => \@B                           
	                       $B->[0] => \&C                           
	         $C variable $resource => \$D                           
	                           $$D => \%Env::Resource::E            
	$Env::Resource::E->{'request'} => \%Plack::Request::F           
	   $Plack::Request::F->{'env'} => \%A