Cant get this to work.

while x ~= "exit" do
 print("-------------------------------")
 print("Main menu:")
 print("Type MFSU and then hit the enter key for MFSU management.")
 print("Type em for energy management.")
 print("Type exit to go back to previous menu.")

 write(" Choose an option now, please.")

 print("-------------------------------")

 x = io.read()

 if x == "MFSU" then


  while y ~= "exit" do

   print("-------------------------------")

   print("MFSU Factory:")

   print("To turn on, type on. To turn off, type off")
   print("to exit from MFSU menu type exit")

   write("")

   print("-------------------------------")

   y = io.read()

   if y == "on" then

	redstone.setOutput("right", true )

	print("------------------------------")

	print("You have chosen to turn the Factory on.")

	elseif y == "off" then

	redstone.setOutput("right", false )

	print("------------------------------")

	print("You have chosen to turn the Factroy off.")

   end -- if y = on/off

  end -- while y

 end -- if MFSU
 if x == "em" then



  while u ~= "exit" do

   print("-------------------------------")

   print("Energy management menu:")

   print("- ")
   print("To turn The Reactor On, type on. To turn the Reactor off type off")
   print("to exit from energy management menu type exit")

   write("")

   print("-------------------------------")

   u = io.read()

   if u == "on" then

	redstone.setOutput("left", true )

	print("------------------------------")

	print("You have chosen to turn the Reactor On.")

   elseif u == "off" then

	redstone.setOutput("left", false )

	print("------------------------------")

	print("You have chosen to turn the Reactor off.")

   end -- if u = on/off

  end -- while u

 end -- if em

end -- while z