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Regular Expressions:Examples

  * .at matches any three-character string ending with "at",

      including "hat", "cat", and "bat".

  * [hc]at matches "hat" and "cat".
  * [^b]at matches all strings matched by .at except "bat".
  * ^[hc]at matches "hat" and "cat", but only at the beginning

     of the string or line.
  * [hc]at$ matches "hat" and "cat", but only at the end

     of the string or line.
  * \[.\] matches any single character surrounded by "[" and "]"

       since the brackets are escaped, for      example: "[a]" and "[b]".
  * [hc]+at matches "hat", "cat", "hhat", "chat", "hcat",

       "ccchat", and so on, but not "at".
  * [hc]?at matches "hat", "cat", and "at".
  * [hc]*at matches "hat", "cat", "hhat", "chat", "hcat", "ccchat",

       "at", and so on.
  * cat|dog matches "cat" or "dog".

For detail explanation: http://en.wikipedia.org/wiki/Regular_expression