Using your example here:

claims = %{"first" => "First claim", "second" => "Second claim"}
names = "first,second"

String.split(names,",")
|> Enum.map(fn(x) -> Map.get(claims,x) end)
|> Enum.join(",")

Output: "First claim,Second claim"

This will only work if the keys in claims are strings, as you mentioned earlier. If the keys were not strings but instead were atoms, then you would need convert them, probably doing something like:

keys = for name <- String.split(names,","), do: String.to_atom(name)

(I’m going to assume that they’re strings.)

However, I think this way is cleaner:

keys = names |> String.split(",")
claims |> Map.take(keys) |> Map.values |> Enum.join(",")

Output: "First claim,Second claim"