old_contents: # coding: utf-8
  """
      regex
      ~~~~~
  
      This is a prototype for an implementation of regular expressions. The goal
      of this prototype is to develop a completely transparent implementation,
      that can be better reasoned about and used in a parser.
  
      Note that as of now "regular expressions" actually means *regular*, so
      non-greedy repetitions (``*?``, ``+?``), positive/negative
      lookahead/-behind assertions are not supported with the current
      implementation. On the other hand this allows for a very efficient
      implementation.
  
      Currently regular expressions can be compiled to NFAs and DFAs (graph and
      table driven).
  
      :copyright: 2012 by Daniel Neuhäuser
      :license: BSD, see LICENSE.rst
  """
  
new_contents: # coding: utf-8
  """
      regex
      ~~~~~
  
      This is a prototype for an implementation of regular expressions. The goal
      of this prototype is to develop a completely transparent implementation,
      that can be better reasoned about and used in a parser. This is not meant
      to be an implementation that will see real-world usage, in fact the
      performance on most - if not all - python implementations will make that
      prohibitive.
  
      Note that as of now "regular expressions" actually means *regular*, so
      non-greedy repetitions (``*?``, ``+?``), positive/negative
      lookahead/-behind assertions are not supported with the current
      implementation. On the other hand this allows for a very efficient
      implementation.
  
      Currently regular expressions can be compiled to NFAs and DFAs (graph and
      table driven).
  
      :copyright: 2012 by Daniel Neuhäuser
      :license: BSD, see LICENSE.rst
  """
  
subject: Add warning about real-world usage