On Fri, Jan 18, 2013 at 6:58 AM, Mimiko <vbvbrj@gmail.com> wrote:
 I try:

<extension name="Loopback Call">
  <condition field="destination_number"
expression="^${pref1}([5-8]\d\d)$" require-nested="true">
   <condition field="${user_exists(id $1 $${domain})" expression="^true$">
    <action application="transfer" data="$1 XML default"/>
   </condition>
  </condition>
  <condition field="destination_number"
expression="^${pref2}([6-8]\d\d)$" require-nested="true">
   <condition field="${user_exists(id $1 $${domain})" expression="^true$">
    <action application="transfer" data="$1 XML default"/>
   </condition>
  </condition>
</extension>

How about:
<extension name="Loopback Call">
  <condition field="destination_number" expression="^(${pref1}|${pref2})([5-8]\d\d)$"/>
  <condition field="${user_exists(id $2 $${domain})" expression="^true$">
    <action application="transfer" data="$2 XML default"/>
  </condition>
</extension>

I think that does pretty much the same thing, but I'm not sure of your exact requirements.

-- 
Steve