Need help with object oriented PERL program that will read in fixed length data files, execute some logic on the data and write output files

Project Description:
The program will be required to read in a 2 input files containing fixed length records. 1 input file has errors in one of the fields. The other input file contains correct values but the record layout is different from the first file. The PERL program is required to update the erroneous fields in the first input file with the correct values from the second input file based on some business rules that I will provide. There are other key fields in the records that will allow us to match the correct records.