sub f { warn };
$Data::Dumper::Freezer = 'f';
require Data::Dumper;
Data::Dumper::Dumper( bless \$_, 'main' );
__END__
Warning: something's wrong at - line 1.

##</code><code>##

$Data::Dumper::Freezer = "DD_freezer" unless defined $Data::Dumper::Freezer;

*{; do { no strict 'refs'; \*{$Data::Dumper::Freezer} } } = sub {
	# serialisation code here
};