{
   s/
      \G
      ( # $1
         (?:
            # Substitution prevented by preceeding ">>"
            >> (?!>) [^\n]* \n >>> [^\n]* \n
         |
            (?! >> ) [^\n]* \n
         )*
      )

      >>>

      ( # $2
         [^\n]* \n
      )

      # Substitution supressed by following ">>".
      (?! >> (?!>))

   /${1}PYTHON_PROMPT${2}/xg;

   print;
   print("==========\n");
}