Grammar of parser regular expression

Hello All,

Is there any document to explain the grammar of parser regular expression? It is similiar to the standard regular expression, but not exactly same.

For example,

(?<DEVICE_TYPE_CODE>[?\w]*)

What does the ? mean?. How to present 5 characters(except \w\w\w\w\w)? How to present 3-5 characters?

Thanks a lot.