example.ex

defmacro example(keys) when is_list(keys) do
  quote do
    example(unquote(keys), defer_to: __MODULE__, loaded: false)
  end
end

defmacro example(keys, defer_to: defer_to) when is_list(keys) do
  quote do
    example(unquote(keys), defer_to: unquote(defer_to), loaded: false)
  end
end

defmacro example(keys, loaded: loaded) when is_list(keys) and is_boolean(loaded) do
  quote do
    example(unquote(keys), defer_to: __MODULE__, loaded: unquote(loaded))
  end
end

defmacro example(keys, defer_to: defer_to, loaded: loaded) when is_list(keys) and is_boolean(loaded) do
  quote do
    real code here
  end
end

usage.ex

defmodule Example do
  import MacroExample
  
  defrandomized([:a, :b, :c])
  defrandomized([:a, :b, :c], defer_to: A)
  defrandomized([:a, :b, :c], loaded: true)
  defrandomized([:a, :b, :c], defer_to: A, loaded: true)
end