loading XML page from another XML page for parsing

for example :

you have an XML file located on a web server called : XML_URL.XML it contains something like

<hls>
http://example.org/example/
</hls>
<userURL>

http://example.org/usersURL/?user=(here is a variable that changes often)
</userURL>

you need to load this URL from another XML file like :

 <item>
         <title>title</title>
 <link>http://myexample.org/?user=$doregex[url]</link>
  <regex>
 <name>url</name>
 <expres>\?user=(.+)</expres>
 <page>http://myexample.com/XML_URL.XML</page>
  </regex>
  <thumbnail></thumbnail>
       </item>

it works with JSON , but its not working when the "page" is XML file

any solutions ?