my $print_rev = sub { print scalar reverse $_[0]; };

Now we have a lexically scoped variable, visible only within its package, containing a reference to an anonymous sub.

Within our class/package, we call it by doing something like:

&$print_rev("Reversed!");

Voila! Instant private method!

note: this is partway to creating closures, which are functions declared at runtime with, with variables passed as parameter. I might mention them some other time.