How would you accumulate errors?

You could reduce each function call… then check if Enum.all?, Enum.any?, whatever tests You may want to run on the list.

# NOT TESTED!

result = ~w(extract_login extract_mail extract_pw)a
|> Enum.reduce(&apply(__MODULE__, &1, [user]))

But your code looks like a user validation, and usually this can be done with a changeset.