The LambdaCase extension

The LambdaCase GHC extension introduces a kind of expression that is something of a cross between a case expression and a lambda.

For example, take this function that converts the l characters in a string to Greek.

λ> putStrLn (lambdaize "Delightful!")
-- Deλightfuλ!

We can write this function more tersely by converting the named function f into a lambda-case expression: