my %TempMap;

sub foo :lvalue {
    my $self= shift;
    my $value= $self->fetch("foo");
    $TempMap{"".\$value}= [$self,"foo"];
    return bless My::Module::Value, \$value;
}

sub My::Module::Value::DESTROY {
    my $svValue= shift;
    my( $self, $name )= @{ $TempMap{$svValue} };
    $self->store( $name, $$svValue );
}