how to read and change <!Doctype> tag and <?xml version="1.0"?> in xml twig?

I'm new to xml twig... how to read and change <!DOCTYPE article SYSTEM "loose.dtd"> and <?xml version="1.0" encoding="UTF-8"?> . how can I modification in this tag.. because i don't know how to this read and change this tag in xml::Twig...

my input:

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE art SYSTEM "loose.dtd">
<art>
<fr>
<p>Text</p>
<p>Text</p>
</fr>
<fr>
<p>Text</p>
<p>Text</p>
</fr>
</art>

I need output as:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<DTD>
<Contents type="&lt;!DOCTYPE article SYSTEM &quot;loose.dtd&gt;"/>
</DTD>
<art>
<fr>
<p>Text</p>
<p>Text</p>
</fr>
<fr>
<p>Text</p>
<p>Text</p>
</fr>
</art>

how can alter <?xml ?> and <!Doctype> tag, can you any one help this process..

Solution

You can try the following (code it's commented). The important point to understand it is to create a new twig, copy all the elements you want to keep and create what it changes:

#!/usr/bin/env perl

use warnings;
use strict;
use XML::Twig;

## Create a twig based in an input xml file.
my $twig = XML::Twig->new;
$twig->parsefile(shift);

## Create a new twig that will be the output.
my $new_twig = XML::Twig->new( pretty_print => 'indented' );

## Create a root tag.
$new_twig->set_root( XML::Twig::Elt->new( 'root' ) );

## Create the xml processing instruction.
my $e = XML::Twig::Elt->new( 'k' => 'v' );
$e->set_pi( 'xml', 'version="1.0" encoding="UTF-8" standalone="yes"' );
$e->move( before => $new_twig->root );

## Copy the whole tree from the old twig.
my $r = $twig->root;
$r->paste( first_child => $new_twig->root );

## Copy the doctype from the old twig to the new one.
my $contents_elt = XML::Twig::Elt->new( Contents  => { type => $twig->doctype } );
my $dtd_elt = XML::Twig::Elt->new( DTD => '#EMPTY' );
$contents_elt->move( last_child => $dtd_elt );
$dtd_elt->move( first_child => $new_twig->root );

## Print the whole twig created.
$new_twig->print;

Run it like:

perl script.pl xmlfile

That yields:

  <?xml version="1.0" encoding="UTF-8" standalone="yes"?><root>
  <DTD>
    <Contents type="&lt;!DOCTYPE art SYSTEM &quot;loose.dtd&quot;>&#x0a;"/>
  </DTD>
  <art>
    <fr>
      <p>Text</p>
      <p>Text</p>
    </fr>
    <fr>
      <p>Text</p>
      <p>Text</p>
    </fr>
  </art>
</root>