menu channel,nicklist {
  Chat Assistant
  .Open:message
  .Auto Chat Assistant
  ..On: noop $input(Auto Chat Assistant is $iif(%autochatassistant == on,already on,now on),o,Auto Chat Assistant) | set %autochatassistant on
  ..Off: noop $input(Auto Chat Assistant is $iif(%autochatassistant == on,now off,already off),o,Auto Chat Assistant) | unset %autochatassistant 
}

Long and usless code, imo. Use:

menu channel,nicklist {
  Chat Assistant
  .Open: message
  .Auto Chat Assistant
  ..$iif(%autochatassistant == on,Off,On): set %autochatassistant $iif(%autochatassistant == on,off,on) | noop $input(Auto Chat Assistant is $iif(%autochatassistant == on,now on,now off),o,Auto Chat Assistant)
}

No offense though ;P