It seems it adds the html and head tags for convenience, you can just get the body like this:

my $body = $root->find('body');
print $body->as_HTML;
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edit: Although, now it seems that the ending /p tags go missing and I am not sure why. Maybe the module is not perfect, try this as a workaround:

my @foo = $html->look_down(
    _tag => "body",
) ;
foreach( @foo ) {
    my $output_html = $_->as_HTML(undef,undef,{});
    print $output_html;
    last ;
}
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