Might work

local yes = ""
local no == ""
local yo == ""
local la == ""

while true do -- start infinite loop
	shell.run("clear")
	print (" Panic Room Door control 0.2v")
	print (" ----------------------------")
	print (" [1] Open Door ")
	print (" [2] Close Door ")
	print (" [3] Exit ")
	print (" [4] Shutdown Computer ")

	a, b = os.pullEvent()
	while a ~= "key" do a,b = os.pullEvent()
		if b == 1 then
			yes = 1
		elseif b == 2 then
			no = 1
		elseif b == 3 then
			yo = 1
		elseif b == 4 then
			la = 1
		end
	end


	if yes == 1 then
redstone.setOutput ("back", false)
redstone.setOutput ("down", false)
shell.run("startup") break -- break loop before continuing
end

if no == 1 then redstone.setOutput ("back", true)
redstone.setOutput ("down", true)
shell.run("startup")
break -- break the loop before proceeding
end

if yo == 1 then sleep(0) -- to avoid an error
if la == 1 then sleep(1)
os.shutdown()
end

end -- end the loop