You should post the code you have tried then we can see something of how you are thinking and can help you much more than just giving you some sort of canned solution that you may not understand and thatmay not actually work will in your actual situation.

When you post your code remember to give a sample of the erronious output and a sample of the output you would like to see.

In the mean time, think hashes. That is, maybe you can slurp the file (if it's not very large) and build a hash using the file name as the key and the extra text as the value. Then processing the array becomes a simple matter of looking up hte file name in the hash and spitting out the result.