Something

on *:TEXT:!setgreet*:#: {
  set %greet [ $+ [ $nick ] ] $2-
  notice $nick Your greet has been set to, " $+ %greet [ $+ [ $nick ] ] $+ "
}

on *:JOIN:#: {
  msg $chan [ $+ $nick $+ ] %greet [ $+ [ $nick ] ]
}

on *:TEXT:!delgreet:#: {
  unset %greet [ $+ [ $nick ] ]
  notice $nick You greet has been unset.
}