I'd consider either exporting the spreadsheets to CSV or TSV format and then the Text::CSV_XS module to access the data, or use the Spreadsheet module to get at the data directly.

For the comma-separated list, you would of course probably be reasonably well-served by the split command, or feed that into a secondary Text::CSV_XS object.

Once everything is in a list, there are a variety of ways to compare the list, but the easiest for a new programmer to understand will probably be looping through an array.

A hash would likely be more execution-efficient, but you would need to understand how to use hashes and you give no indication of having that level of experience.