How can I execute StateT monad with IO?

I am trying to follow the guidelines in Combine State with IO Actions to create an AppState along with an I / O monad. I got it:

module Main where

import Control.Monad.State
import Control.Monad.Trans

data ST = ST [Integer] deriving (Show)
type AppState = StateT ST IO

new = ST []

append :: Integer -> State ST ()
append v = state $ \(ST lst) -> ((), ST (lst ++ [v]))

sumST :: State ST Integer
sumST = state $ \(ST lst) -> (sum lst, ST lst)

script = do
    append 5
    append 10
    append 15
    sumST

myMain :: AppState ()
myMain = do
    liftIO $ putStrLn "myMain start"
    let (res, st) = runState script new
    liftIO $ putStrLn $ show res
    liftIO $ putStrLn "myMain stop"

main = runStateT myMain (ST [15])

There, I don’t get any part of it. I am very worried that I have scriptand myMainand main. It also bothers me what I have to execute runStateinternally myMainand that I need to pass the initial state to in runStateTin my main function. I want to have a "script", so to speak, directly in the myMain function, because the whole point of myMain should be able to start adding and summing directly in myMain and right next to the print operations. I think I could do this instead:

myMain :: AppState ()
myMain = do
    liftIO $ putStrLn "myMain start"
    append 5
    append 10
    append 15
    r <- sumST
    liftIO $ putStrLn $ show res
    liftIO $ putStrLn "myMain stop"

main = runState myMain

, - , (, ) - . , ?

( ), , . -, myMain main:

myMain :: AppState ()
myMain = do
    liftIO $ putStrLn "myMain start"
    append 5
    append 10
    append 15
    res <- sumST
    liftIO $ putStrLn $ show res
    liftIO $ putStrLn "myMain stop"

main = runStateT myMain new

append sumST, Daniel's:

append :: Integer -> AppState ()
append v = state $ \(ST lst) -> ((), ST (lst ++ [v]))

sumST :: AppState Integer
sumST = state $ \(ST lst) -> (sum lst, ST lst)

( , , !)

append :: MonadState ST m => Integer -> m ()
append v = state $ \(ST lst) -> ((), ST (lst ++ [v]))

sumST :: MonadState ST m => m Integer
sumST = state $ \(ST lst) -> (sum lst, ST lst)

, AppState/StateT , sumST, . - StateT, , (, runState script new).

, , , MonadState - , .