This means "match a subpattern, but don't include the match in the back-references." So let's examine the subexpression

这表示“查找子模式的匹配字符串，但不包括反向引用中的匹配结果”。

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The POSIX standard does not support back-references for "extended" regular expressions, this is a compatible extension to that standard.

POSIX标准并不支持“扩展”正则表达式的后向引用，这是对标准的兼容扩展。

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This Web service application will enable users to upload any number of files to the server and get references back to those files, as well as download the files they want using these references.

这个Web服务应用程序将使用户能够向服务器上传任意数量的文件，获得对这些文件的引用，还可以使用这些引用下载他们想要的文件。

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Wired.com reported in August that Griffith created an application called WikiScanner that tracks edits that have been made to Wikipedia articles and cross-references them against IP addresses, which can be traced back to companies' offices.

CNN: Use with caution: The perils of Wikipedia

Professor Rajan Gerta, from Mahatma Gandhi University in Kerala, said that there are many references to "ships coming with gold, and going back with 'black gold'" - pepper.

BBC: NEWS | South Asia | Search for India's ancient city