Yes, each file has the first column of the first file, however the other files can have multiple instances of it. eg: 1st file: perl book,writer:xxxx,publisher:xxxx 2nd file: perl book,first edition,$29.99 2nd file: perl book,second edition,$25.99 3rd file: perl book,third edition,$x big file: perl book,writer:xxxx,publisher:xxxx||first edition,$29.99||second edition,$25.99||third edition,$x