> perl -MData::Dumper -e "unshift @arr, sub { print 'hi' }; print Dumper \@arr"
$VAR1 = [
          sub { "DUMMY" }
        ];

> perl -MThread::Queue -MData::Dumper -e "$q = new Thread::Queue; $q->enqueue(sub { print 'hi'}); print Dumper $q"
$VAR1 = bless( [
                 sub { "DUMMY" }
               ], 'Thread::Queue' );