When in Drupal you upload a file with the same filename a new file name is created with _.. The regexp is made to filter the supposedly original filename. After checking existence and filelength match the presuppostion is confirmed and deduplication takes place.

There too many images that don't fit the category. I had to put this regexp to have higher change finding them.

This is a regex for the above mentioned data clean up

valid mails abc@yahoo.com abc-100@yahoo.com abc.100@yahoo.com abc111@abc.com abc-100@abc.net...