Thanks, your comment made me, finally, realize the error in my code

First I want to apologize for not posting correct code, but I am unable to disclose the code i am workning with right now

So, the problem rised when in the object I had..

sub new
{
  ...
  $self = {
      ...
      _IP => undef,
      ...
  }
  bless ($self, $class);
  return $self;
}

sub set_ip
{
  my ($self,$ip) = @_;
  $self->{_IP} = new Net::IP($ip) or die (Net::IP::Error());
}
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The problem here is that Net::IP does not overload the method '==' so XMLout explodes at line 1406 in Simple.pm.

if(grep($_ == $ref, @{$self->{_ancestors}}));
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You can see this line is trying to look for references to the present node (circular references)

So either a) overload '==' at XML::Simple b) Instead of using Net::IP use simple strings c) comment lines 1405 and 1406

Thanks