network script broken for vlan devices

network script shows 0kB/s all the time for vlan devices (and probably for any network device that's longer than 6 characters).

offending line(s) in /usr/lib/byobu/network:
  x2=`grep -m1 "\W$interface:" /proc/net/dev | sed "s/^.*://" | awk '{print $9}'`

\W matches a non-word character before the interface name. For device names longer than 6 chars there isn't any.
$ grep -m1 "\Wvlan1000:" /proc/net/dev

Maybe match the word boundary if you must:
$ grep -m1 "\bvlan1000:" /proc/net/dev
vlan1000:164329464828 144006418 0 0 0 0 0 20 133694577772 76407553 0 0 0 0 0 0