atom feed: script to combine multiple <author> items into one?

I would like to write a command line script which combines multiple <author> tags from an atom feed into one. For example, an entry like:

<entry>
    <id>someid</id>
    <published>somedate</published>
    <title>Title</title>
    <summary>Summary</summary>
    <author>
      <name>Author One</name>
    </author>
    <author>
      <name>Author Two</name>
    </author>
    <author>
      <name>Author Three</name>
    </author>
  </entry>

should become:

<entry>
    <id>someid</id>
    <published>somedate</published>
    <title>Title</title>
    <summary>Summary</summary>
    <author>
      <name>Author One, Author Two, Author Three</name>
    </author>
  </entry>

I think I could do it myself using Perl and regexes but, as parsing XML with regexes is not a good idea, I would be thankful for a more elegant solution that uses a proper xml-parser.

Ted has the right idea, but a few things were done in a more complicated manner than needed, and they were unaware of the properties of the Atom format (e.g. its use of namespaces).

use XML::LibXML               qw( );
use XML::LibXML::XPathContext qw( );

my $xpc = XML::LibXML::XPathContext->new();
$xpc->registerNs(a => 'http://www.w3.org/2005/Atom');

# See XML::LibXML::Parser for more ways to create the document object.
my $doc = XML::LibXML->load_xml( location => 'atom.xml' );

for my $entry_node ($xpc->findnodes('/a:feed/a:entry', $doc)) {
   my @author_names;
   for my $author_node ($xpc->findnodes('a:author', $entry_node)) {
      push @author_names, $xpc->findvalue('a:name', $author_node);
      $author_node->unbindNode();
   }

   my $author_node = XML::LibXML::Element->new('author');
   my $name = $author_node->appendTextChild('name', join(", ", @author_names));
   $entry_node->appendChild($author_node);
}

$doc->toFile('atom.new.xml');