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  <library>
    <book>
...
             width="100" height="125" />
    </book>
  </library>

  #!/usr/bin/perl

...
  use warnings;

  my $filename = 'library.xml';

  use XML::Simple qw(:strict);

...
  foreach my $book (@{$library->{book}}) {
    print $book->{title}->[0], "\n" 
  }

  use XML::LibXML;

...
    my($title) = $book->findnodes('./title');
    print $title->to_literal, "\n" 
  }

  foreach my $title ($doc->findnodes('/library/book/title')) {
    print $title->to_literal, "\n" 
  }

  print $_->data . "\n" foreach ($doc->findnodes('//book/title/text()'
+));

  use XML::Simple qw(:strict);

...

  my $book = $library->{book}->{$isbn};
  print "$_\n" foreach(@{$book->{author}});

  use XML::LibXML;

...
  my $query  = "//book[isbn/text() = '$isbn']/author/text()";

  print $_->data . "\n" foreach ($doc->findnodes($query));

  my $library  = XMLin($filename, ForceArray => [ 'book' ], KeyAttr =>
+ {});

  foreach my $book (@{$library->{book}}) {
    print $book->{isbn}, "\n" if $book->{pages} > 900;
  }

  use XML::Simple qw(:strict);

...
  $book->{pages}->[0] = '394';

  print $xs->XMLout($ref);

  use XML::LibXML;

...
  $node->setData('394');

  print $doc->toString;

  my($book)  = $doc->findnodes("//book[isbn = '$isbn']");
  my $library = $book->parentNode;
  $library->removeChild($book);

  my $rating = $doc->createElement('rating');
  $rating->appendTextNode('5');
  $book->appendChild($rating);

  $book->appendTextChild('rating', '5');

  my $fragment = $parser->parse_balanced_chunk(
    '<rating>5</rating><price>32.00</price>'
  );
  $book->appendChild($fragment);

  xmllint --format -