Mine

on *:text:!away*:#:{
  if (%away. [ $+ [ $nick ] ] == $null) {
    set %away. [ $+ [ $nick ] ] $iif($2,$lower($2-),away)
    set %awaytm. [ $+ [ $nick ] ] $ctime
    set %awaynick. [ $+ [ $nick ] ] $lower($nick)
    msg $chan 4 $lower($nick) 10is now away, Reason:4 %away. [ $+ [ $nick ] ] $+ 10.
  }
  else notice $nick your away :l
}
on *:text:!back:#:{
  if (%away. [ $+ [ $nick ] ] != $null) {
    msg $chan 4 $lower($nick) 10back from:4 %away. [ $+ [ $nick ] ] $+ 10. Time away:4 $duration($calc($ctime - $eval($+(%,awaytm.,$nick),2))) $+ 10.
    unset %away. [ $+ [ $nick ] ]
    unset %awaynick. [ $+ [ $nick ] ]
    unset %awaytm. [ $+ [ $nick ] ]
  }
  else notice $nick your not away
}