We use the let keyword to give an expression a name by which we can refer to it later.
If we let x equal 2, then x plus x equals 4.
let x = 2
putStrLn (show (x + x))
You can define multiple variables at once.
let (b, c) = ("one", "two")
You can also define multiple variables within a single let clause.
d = True
e = [1,2,3]
putStrLn (show d)
putStrLn (show e)
$ runhaskell variables.hs