or you can also do

menu channel,menubar {
  .Greet
  ..Set Greet Chan: { $$?="Enter Channel. i.e. #scripts" | set %greetchan $iif($left($!,1) != $chr(35),$+($chr(35),$!),$!) | echo -a Greet Channel Is Now Set As %greetchan }
  ..Turn Greet $iif($group(#greet) = on,Off,On):{ $iif($group(#greet) = off,.enable,.disable) #greet | echo -a Greet Is Now $group(#greet) In Channel %greetchan }
}
#greet on
on !*:JOIN:%greetchan:.timeropcheck 1 1 opcheck $nick # 
alias -l opcheck if ($nick($2,$1,hvr)) .notice $1 7 $1 Welcome to $v2 11 Have a nice 7 Chat
on !*:part:%greetchan:if ($nick(%greetchan,$nick,hvr)) .notice $nick 7 $nick You left from %greetchan 11 cu 7 later 
#greet end

just one of many diff ways you can make this.....