package Persist;

...

sub uuid {
	# returns a unique ID for the object. should be
	# overridden by the subclass
};

sub load 
	# load object from persistent store
	$self->{_change} = 0;
};

sub save {
	my $self = shift;
	return unless $self->{_change};
	# save object to persistent store
	$self->{_change} = 0;
};

sub mark {
	my $self = shift;
	# mark and item as changed so it should be saved
	$self->{_change}++;
};