"And you will get very strange effects as soon as closures start playing a role."

Here is thospel's strange effects ;-)

do_this("abc\n");
do_this("123\n");

sub do_this {  
    my $msg = shift;
    new_sub(); 
      sub new_sub
      {
            print $msg;
      }    
}
[download]

This prints:

abc
abc
[download]