   defp do_at(nil, _, _), do: nil
 
   @doc """
-  Returns a substring starting at the offset given by the first, and
-  a length given by the second.
+  Returns a substring starting at the offset `start`, and of
+  length `len`.
 
   If the offset is greater than string length, then it returns `""`.
 
-  Remember this function works with unicode codepoints and considers
-  the slices to represent codepoints offsets. If you want to split
+  Remember this function works with Unicode codepoints and considers
+  the slices to represent codepoint offsets. If you want to split
   on raw bytes, check `Kernel.binary_part/3` instead.
 
   ## Examples

  end

  @doc ~S"""
  Returns a new binary based on `subject` by replacing the parts
  matching `pattern` by `replacement`. By default, it replaces
  all entries, except if the `global` option is set to `false`.

  A `pattern` may be a string or a regex.

  ## Examples


  is traversed first in order to convert the negative indices into
  positive ones.

  Remember this function works with Unicode codepoints and considers
  the slices to represent codepoints offsets. If you want to split
  on raw bytes, check `Kernel.binary_part/3` instead.

