I made this for you, if i understand right you want to ask any new user there age, and if they have been on the channel 1 time before, then you just want to great them with a welcome message? here we go:
Code:
on *:join:#: {
  if ($nick != $me) && ($chan == #chat18+) {
    if (!$isfile($+(join.txt))) { write join.txt }
    if ($nick isin $read(join.txt, w, $+(*,$nick,*))) { describe $Chan Hey $nick $+ , Welcome Back. :)    }
    else {
      describe $chan Hello $nick $+ , Welcome to $chan $+ . May we have your age Please ?
      write join.txt $nick
    }
  }
}

This will create the file join.txt first time someone join the channel, then it will add the nick to the txt file, and after that it will scan the file, if a nick is in the text file. then it will just great the user, if a user are new, then it will add the user and ask for the age, and next time he join it will be a great with welcome. hope this is what you looking for.

if ($me != tired) { return } | else { echo -a Get a pot of coffee now $+($me,.) }