use strict;
use warnings;

use Devel::Peek  qw( Dump );
use Scalar::Util qw( blessed );
use XML::Writer  qw( );

my $writer = new XML::Writer(OUTPUT => \my $doc);
$writer->startTag("root");
$writer->startTag("foo");
$writer->endTag("foo");
$writer->endTag("root");
$writer->end();

Dump $doc;
print(blessed(\$doc)?1:0, "\n");   # 1

my $copy = $doc;

Dump $copy;
print(blessed(\$copy)?1:0, "\n");  # 0