Someone

on *:JOIN:#: {
  if (%whois [ $+ [ $chan ] ] == on) {
    whois $nick
    set %msgchan msg $chan
    set %nick $nick
  }
}
raw 319:*:{
  %msgchan 1 %nick is on the following channels: 12 $3-
  unset %msgchan
  unset %nick
}

on *:TEXT:!whois on*:#: {
  if ($nick isop $chan) || ($nick ishop $chan) {
    if (%whois [ $+ [ $chan ] ] == on) {
      notice $nick 12Whois check is already on for $chan
    }
    else {
      set %whois [ $+ [ $chan ] ] on
      msg $chan 4 Whois check is now 12ON4 for $chan
    }
  }
}
on *:TEXT:!whois off*:#: {
  if ($nick isop $chan) || ($nick ishop $chan) {
    if (%whois [ $+ [ $chan ] ] == off) { 
      notice 12 $nick it isn't even on in $chan
    }     
    else { 
      set %whois [ $+ [ $chan ] ] off
      msg $chan 4 Whois check is now 12OFF4 for $chan
    }  
  }
}