oh.. or you can have a variable, i.e. -

alias rc { set %rc on }

on *:input:*:{ 
  if (%rc == on) {
    if (! isin $1) return
    if (/ isin $1) return
    if (@ isin $1) return
    tokenize 32 $1- 
    msg $chan  $+ $rand(2,15) $+ $1-
    halt
  }
}

alias rcoff { unset %rc }