# 4 GHz, CentOS 7 ( Perl v5.16.3 )

$ perl foo1.pl | wc -l      # Foo::Inbox
duration: 12.685 seconds
   1600000

$ perl inbox.pl | wc -l     # MCE::Inbox w/ blocking capability
duration: 15.939 seconds
   1600000

$ perl foo2.pl | wc -l      # MCE::Shared->queue
duration: 21.533 seconds
   1600000

$ perl foo4.pl | wc -l      # Thread::Queue
duration: 90.015 seconds
   1600000