This particular issue is with a binary (i.e. pre-built) package, normally in Arch it's expected from an AUR package that you will build it yourself and most if not all packagers prompt you to review and or edit the PKGBUILD before it does anything.

Basically you could spot something suspicious in a source package, not so much in a binary package.

I just hope that "h :ets" works in iex later (for those who don't know, it shows the help/module/function documentation of the value specified)

For the email validation I would have used an ecto schema, since most cases you won't just be validating an email address in isolation:

  defmodule EmailSchema do 
    use Ecto.Schema

    import Ecto.Changeset

    @primary_key false

    embedded_schema do 
      # here is your type validation right off the bat
      field :email, :string
    end

    def validate(email) do
      %__MODULE__{}
      |> cast(params, [
        :email,
      ])
      |> validate_required([
        :email,
      ])
      |> validate_change(:email, fn :email, value ->
        cond do
          not is_email_address?(value) ->
            [email: {"invalid email address", [validation: :email]}]

          not EmailAddresses.is_available?(value) ->
            [email: {"is unavailable", [validation: :email]}]

          true ->   
            []
        end
      end)
      |> apply_action(:insert)
    end
  end

  case EmailSchema.validate(email) do 
    {:ok, %{email: email}} ->

    {:error, %Ecto.Changeset{} = changeset} ->
      changeset.errors[:email] 
      # Can be all of these in the same list, or be any one depending on the validations
      #=> [{"is required", [validation: :required]}]
      #=> [{"invalid email address", [validation: :email]}]
      #=> [{"is unavailable", [validation: :email]}]
  end

For personal projects? Ruby and Elixir, though ruby's documentation has fallen off of shape as of late, that or Elixir's has spoiled me by setting higher bar

I see you mentioned RoR, you can try Phoenix in its place for Elixir.