my $private_method = sub {
    my ($self) = @_;
    . . . 
};

$self->$private_method();

##</code><code>##

{
    my $very_private_method = sub {
        my ($self) = @_;
        . . . 
    };
    $self->$very_private_method(); # Can call it here
}

# But this is a compile error under "use strict 'vars'"
$self->$very_private_method();