Something

on $*:text:/^[@!](brb|bbl)/Si:#:{
  if (%away [ $+ [ $nick ] ] == $null) {
    if ($2 == $null) {
      set %away [ $+ [ $nick ] ] 1
      set %time [ $+ [ $nick ] ] $ctime
      msg $chan  $+ $nick will be right back. Left at $time $+ .
    }
    elseif ($2 != $null) {
      set %away [ $+ [ $nick ] ] $nick
      set %time [ $+ [ $nick ] ] $ctime
      set %reason [ $+ [ $nick ] ] $2-
      msg $chan  $+ $nick will be right back. Left at $time $+ . Reason: $2-
    }
  }
}
on *:TEXT:*:#: {
  if (%away [ $+ [ $nick ] ] == $nick) {
    if (%reason [ $+ [ $nick ] ] == $null) {
      msg $chan  $+ $nick has returned. Gone for: $duration($calc($ctime - %time [ $+ [ $nick ] ]))
    }
    elseif (%reason [ $+ [ $nick ] ] != $null) {
      msg $chan  $+ $nick has returned. Gone for: $duration($calc($ctime - %time [ $+ [ $nick ] ])) $+ . Reason: %reason [ $+ [ $nick ] ]
      unset %reason [ $+ [ $Nick ] ]
    }
    unset %time [ $+ [ $Nick ] ]
    unset %away [ $+ [ $Nick ] ]
  }
}