use strict;
use warnings;

use Data::Dumper;
use XML::Simple;

# The fastest existing backend for XML::Simple.
local $XML::Simple::PREFERRED_PARSER = 'XML::Parser';

my $xs = XML::Simple->new(
   NoAttr         => $ARGV[0],
   KeepRoot       => 1,
   NormaliseSpace => 1,
);

my $tree = $xs->parse_string( <<'__EOI__' );
<BILLING>
 <ACCOUNT></ACCOUNT>
 <RTN></RTN>
</BILLING>
__EOI__

print( Dumper( $tree ) );

print( $xs->XMLout( $tree ) );