Hi, the use of ^^^ is now deprecated
So, from this

$ iex
iex(1)> use Bitwise
Bitwise
iex(2)> key = 2491717835680677893
2491717835680677893
iex(3)> cipher = fn word, key → Enum.map(word, & rem(&1 ^^^ key, 32768)) end
#Function<13.126501267/2 in :erl_eval.expr/5>
iex(4)> List.to_string(cipher.(‘LIjs`B`k`qlfDibjwlqmhv’, key))
“ILoveGeneticAlgorithms”

To this:

Interactive Elixir (1.12.1) - press Ctrl+C to exit (type h() ENTER for help)
iex(1)> use Bitwise
Bitwise
iex(2)> key=8836176395766890501
8836176395766890501
iex(3)> cipher = fn word, key → Enum.map(word, &rem(bxor(&1, key), 32768)) end
#Function<43.40011524/2 in :erl_eval.expr/5>
iex(4)> List.to_string(cipher.(‘LIjs`B`k`qlfDibjwlqmhv’, key))
“ILoveGeneticAlgorithms”
iex(5)>