Is there a way of referencing captured regex in the first condition of nested conditions?

EG If I have:

    <extension name="8 prefix" continue="true">

      <condition field="destination_number" expression="^8(0\d{9,15})"/>

      <condition field="${db(exists/${sip_from_user}/cli8}" expression="true">

        <action application="set" data="destination_number=$1" inline="true"/>

      </condition>

    </extension>

At the moment this doesn’t capture the number, and just gives me an actual ‘$1’. I guess I could rearrange the conditions, but I don’t want to break all my logic really…