Scalar ≈ IORef

my $a  = 1;  # Haskell: a <- newIORef 1                 -- a :: IORef Int
my $b := 1;  # Haskell: let b = 1                       -- b :: Int
my $c  = $a; # Haskell: c <- newIORef =<< readIORef a   -- c :: IORef Int
my $d := $a; # Haskell: let d = a                       -- d :: IORef Int

put "$a$b"; # Haskell: s <- (<>) <$> readIORef a <*> pure b      ; putStrLn s
put "$c$d"; # Haskell: s <- (<>) <$> readIORef c <*> readIORef d ; putStrLn s