[Freeswitch-users] regex groups

I wrote up a quick dialplan and intended on using $0 for the whole number, so my regex was: <condition field="destination_number" expression="^0\d+$"> but $0 was empty until I rewrote it: <condition field="destination_number" expression="^(0\d+)$"> Is this expected, I assumed not and I was not looking for $1 etc I figured $0 to always get populated. Thanks, jlc