HelloWorld.hs@:0:53: error:

[Crojav]

runghc -XOverloadedStrings simHelloWorld.hs@
Warning: ignoring unrecognised input `simHelloWorld.hs@'

simHelloWorld.hs@:0:53: error:
    • Variable not in scope: main :: IO a0
    • Perhaps you meant ‘min’ (imported from Prelude)

This is not the only errors I get:
From the https://hackage.haskell.org/package/simple

$ cabal install simple
$ smpl create my_app_name
$ cd my_app_name
$ smpl

$ ls
Application.hs Main.hs MyAppName my_app_name.cabal

$ smpl
smpl: wai-handler-devel: rawSystem: runInteractiveProcess: exec: does not exist (No such file or directory)

We try to solved this issue without success on https://discourse.haskell.org/t/network-http-simple-wai-handler-devel-does-not-exis/1050

Not easy to say, this is not the first errors i get in starting with Haskell, what I found is that most documentation, blog post, official sites are not well maintained.

[alevy]

You need to have wai-handler-devel installed and on your path to run in development mode (which reloads and recompiles the application automatically whenever you modify the source).