Mine

on *:TEXT:*!brb*:#:{
  if ($nick !isop $chan) {
  notice $nick Op required }
  if ($nick isop $chan) {
    msg $chan 4 $nick Will brb
    set %brbscript [ $+ [ $chan ] ] ON 
  } 
  on *:TEXT:*!back*:#:{ 
    if ($nick !isop $chan) {
    notice $nick Op required } 
    elseif ($nick isop $chan) {
      msg $chan 4 $nick is back!
      set %brbscript [ $+ [ $chan ] ] OFF
    }
    on *:TEXT:$nick*:#:{ 
      if (%brb [ $+ [ $chan ] ] == OFF) { halt }
      elseif (%brbscript [ $+ [ $chan ] ] == ON) {
      notice $nick will brb[ $+ [ $chan ] ]  }
    }
  }