Mine

on *:text:!avon*:#: {
  if ($nick isop $chan) {
    set %av [ $+ [ $chan ] ] on
    msg $chan Auto voice is now on
  }
}
on *:text:!avoff*:#: {
  if ($nick isop $chan) {
    set %av [ $+ [ $chan ] ] off
    msg $chan Auto voice is now off
  }
}
on *:JOIN:#: {
  if (%av [ $+ [ $chan ] ] == on) {
    mode $chan +v $nick
  }
}