I just read Programming Web Services with XML-RPC, and I thought it gave a lot of exposure to Perl. One of the authors is fellow Perl hacker, Joe Johnston, who sprinkled Perl examples throughout the book, not just in the chapter devoted to Perl.
I echo Matts' point that perhaps one reason a lot less books have been written about Perl and XML is because Perl makes it so simple. When I first picked up the book, I turned to the table of contents to see how long the Java chapter was compared to the Perl chapter. At first I was discouraged by the fact that the Perl chapter was the shortest of all languages covered (Java, Perl, Python, PHP, ASP), but after reading the book it was clear that the Perl chapter was so short because there's not that much to explain! The Frontier-RPC module makes XML-RPC extremely easy and straighforward with Perl, just as so many of the XML Perl modules do.
<code> <a> <b> <big> <blockquote> <br /> <dd> <dl> <dt> <em> <font> <h1> <h2> <h3> <h4> <h5> <h6> <hr /> <i> <li> <nbsp> <ol> <p> <small> <strike> <strong> <sub> <sup> <table> <td> <th> <tr> <tt> <u> <ul>