Hi, thanks for the answer, Yes I am calling set_xml with an XMLin result as follows:

 
my $parser = new XML::Simple;
$o->set_xml($parser->XMLin($data));
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As you guess, I am far to be a perl expert, What do you mean saying 'Set your Moose type constraint accordingly ' ? Is it possible to return a pure XML::Simple object, or this means nothing in perl ? Thanks !