Computercraft login system with redstone output

shell.run("clear")
print("Lab Secure Access")
local u1username = "user1" -- set me
local u1password = "pass1" -- set me
local u2username = "user2" -- set me
local u2password = "pass2" -- set me
repeat
  write("Enter Your Name: ")
  local status1, username = pcall(read)
  write("Enter Your Password: ")
  local status2, password = pcall(read, "*")
until (username == u1username or username == u2username) and (password == u1password or password == u2password)
print("Welcome Back")
redstone.setOutput("left", true)
pcall(sleep, 5)
redstone.setOutput("left", false)
shell.run("shutdown")