shaneny, I don't see why:

on *:TEXT:$($iif(!greet* iswm $strip($1),$1)):#:{
  tokenize 32 $strip($1-)
  if ($nick isop $chan) && (!%p) { inc -u3 %p
    if ($2 == set) && ($3-) {
      %greetmsg- [ $+ [ $chan ] ] = $3-
      msg $chan Greet for $chan set to %greetmsg- [ $+ [ $chan ] ]
    }
    elseif ($2 == off) && (%greet- [ $+ [ $chan ] ] == true) {
      unset %greet- [ $+ [ $chan ] ]
      msg $chan Greet DEACTIVATED for $chan
    }
    elseif ($2 == on) && (%greetmsg- [ $+ [ $chan ] ]) {
      %greet- [ $+ [ $chan ] ] = true
      msg $chan Greet message for $chan ACTIVATED
    }
    else {
      msg $chan Before activating the greet message please set the message, by typing !greet set (message)
    }
  }
}

I didn't make extensive changes to your current script.