Raw String Question

[Jim Garrison]

I'm an experienced Perl developer learning Python, but I seem to
be missing something about raw strings.  Here's a transcript of
a Python shell session:

  Python 3.0 (r30:67507, Dec  3 2008, 20:14:27) [MSC v.1500 32 bit 
(Intel)] on win32
  Type "copyright", "credits" or "license()" for more information.

      ****************************************************************
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      makes to its subprocess using this computer's internal loopback
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      interface and no data is sent to or received from the Internet.
      ****************************************************************

  IDLE 3.0
  >>> r"a\b"
  'a\\b'
  >>> r"a\"
  SyntaxError: EOL while scanning string literal (<pyshell#45>, line 1)
  >>> r"a\ "
  'a\\ '
  >>> r"a\""
  'a\\"'

It seems the parser is interpreting the backslash as an escape
character in a raw string if the backslash is the last character.
Is this expected?