package Foo;

sub _my_private_method { ... };

# we can just call it as a subroutine, then no matter
# what methods the subclass define we're okay.
sub my_public_method1 {
	my $self = shift;
	...
	_my_private_method($self); 
	...
};

# We can also root the method call in the current
# class
sub my_public_method2 {
	my $self = shift;
	...
	$self->Foo::_my_private_method;
	...
};