[Haskell-beginners] How to include {-# LANGUAGE LambdaCase #-} at the ghci prompt

[Galaxy Being]

I've got this code I've entered into the ghci by hand between :{ and :}

:{
{-# LANGUAGE LambdaCase #-}
data List a = Empty | Cons a (List a) deriving (Eq, Ord, Show)
infixr 5 `Cons`

subst_c :: (a -> Bool)  -> (a, MyList a) -> MyList a
subst_c pred = \ case
                     (_, Empty)    -> Empty
                     (n, Cons e t)
                       | pred e    -> Cons n $ subst_c pred (n, t)
                       | otherwise -> Cons e $ subst_c pred (n, t)
:}

but I keep getting the error

Illegal lambda-case (use -XLambdaCase)

This works fine inside an .hs file and :load and run at the prompt.
However, I'm using Emacs org-mode and need to keep everything limited to a
version of hand-entered :{ ... :}. Any suggestions?

LB
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.haskell.org/pipermail/beginners/attachments/20210326/1fc0b93c/attachment.html>