Comment by trealira

Yes, and AFAIK, you're pretty much free to cause side-effects in functional languages; it's just a bit awkward and somewhat discouraged. It's kind of like how C still has goto, yet it's still a structured programming language.

Even in Haskell, which tries to control side-effects more, it's not hard; it's just that it's stuck with an "IO" annotation. Any function that calls an IO function also becomes an IO function; it's infectious.

  main :: IO ()
  main = putStrLn "hello, world"