在Windows中，如何比较两个文件并仅返回第一个文件中最初存在的第二个文件中缺少的记录？

At regular intervals we are receiving CSV files from an external source that we have little control over. These files are complete sets of current records; however, any records that have been deleted since the previous are not present. We would like to compare the two files and create a separate file of deleted records so we can do some additional processing on them. In an application in another area we have a commercial sort package (CoSort) that does this out of the box; however, we don't have access to that here. The volumes aren't that large, though, and it seems like this is something that standard or free tools might be able to handle quite easily. Ideally this would take the form of a Windows batch file, but Perl or awk solutions would be okay too. Example input files:At regular intervals we are receiving CSV files