IPAddr#zone_id=

# File tmp/rubies/ruby-4.0.0/lib/ipaddr.rb, line 535
def zone_id=(zid)
  if @family == Socket::AF_INET6
    case zid
    when nil, /\A%(\w+)\z/
      @zone_id = zid
    else
      raise InvalidAddressError, "invalid zone identifier for address"
    end
  else
    raise InvalidAddressError, "not an IPv6 address"
  end
end