Basically conforms to GNU wc.
$ stack build
$ cat example.txt | stack exec wc-exe
9 461 3079
$ stack exec wc-exe example.txt
9 461 3079 example.txt
$ stack exec wc-exe example.txt example2.txt
9 461 3079 example.txt
30 225 1529 example2.txt
39 686 4608 total