Something

alias massinvite {
  if (!$2) {
    echo -a /massinvite invited-channel channel
    halt
  }
  elseif ($me !ison $1) || ($me !ison $2) {
    echo -a You must be on both channels to perform the mass invite!
    halt
  }
  else {
    var %nick.add 1
    var %chan.inv $1
    var %chan.inv.to $2
    while (%nick.add <= $nick(%chan.inv,0)) {
      invite $nick(%chan.inv,%nick.add) %chan.inv.to
      inc %nick.add
    }
  }
}