Clarify that byte-oriented interfaces are not touched.

Add example showing script-level usage of the error handler.

pep-0383.txt

@@ -88,6 +88,10 @@ strict definition of UTF-8 to determine what an invalid byte is
 (which, among other restrictions, disallows to encode surrogate codes
 in UTF-8).
 
+Byte-orientied interfaces that already exist in Python 3.0 are not
+affected by this specification. They are neither enhanced nor 
+deprecated.
+
 Discussion
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@@ -106,7 +110,15 @@ open(), which then encodes them back into their original byte
 representation. Applications that need to process the original byte
 strings can obtain them by encoding the character strings with the
 file system encoding, passing "python-escape" as the error handler
-name.
+name. For example, a function that works like os.listdir, except
+for accepting and returning bytes, would be written as::
+
+  def listdir_b(dirname):
+      fse = sys.getfilesystemencoding()
+      dirname = dirname.decode(fse, "python-escape")
+      for fn in os.listdir(dirname):
+          # fn is now a str object
+          yield fn.encode(fse, "python-escape"
 
 Copyright
 =========