title: Can a regex return a match that's not a part of the original string?
body: <p>I'm using an application that requires me to provide a regex for various files. It uses the matches from the regex to uniquely identify each file and then use a data store to retrieve metadata about these files.</p>
  
  <p>there is however a problem with the application, so it assumes that the data which is used to identify each file is only numeric data. Hence, it stores the results of matches in integers. </p>
  
  <p>I control the data store but not the names of the files. Since the application has a bug in it, I was hoping that I could use an encoding scheme to convert the non-numeric data to an integer. But for that I'd require the regex to return something that's not part of the original string as a match. Is this possible? </p>
  
  <p><strong>Edit:</strong> since my question was unclear. I'm not using a programming language. I'm just editing a configuration file. But the application is written in C++. I don't know what specific regex implementation they are using. But I guess it's not possible then. </p>
  
  <p>The reason I asked the question is sql for example allows me to return something that's not part of any table. I was hoping there might be something similar with regex.</p>