POS: A
$CODE1 = sub {
           package Foo;
           use warnings;
           use strict 'refs';
           my $param = shift @_ || '';
           print "Message is: $param\n";
         };
Message is: Please display this message
POS: B
$CODE1 = sub {
           package Foo;
           use warnings;
           use strict 'refs';
           return;
         };