#! perl -slw
use strict;
use XML::Simple;

my $xml = XMLin( \*DATA );
print XMLout( $_, NoAttr => 1, RootName => 'book' ) for @{ $xml->{book} };

__DATA__

##</code><code>##

C:\test>junk
<book>
  <author>Book 1 author 1</author>
  <author>Book 1 author 2</author>
  <isbn>Book1ISBN</isbn>
  <title>Book 1 title</title>
</book>

<book>
  <author>Book 2 author 1</author>
  <author>Book 2 author 2</author>
  <isbn>Book2ISBN</isbn>
  <title>Book 2 title</title>
</book>

<book>
  <author>Book 3 author 1</author>
  <author>Book 3 author 2</author>
  <author>Book 3 author 3</author>
  <isbn>Book3ISBN</isbn>
  <title>Book 3 title</title>
</book>