I know you are hoping that we might just write the whole thing for you, but you should at least show some effort. Meet us part way by showing a first attempt at solving the problem with comments indicating where you can't figure stuff out.

A few hints are in order:

1. Read each file once into a suitable data structure. For the config file that might just be a string. For the game list it's probably an array.
2. Iterate over the items in the game list and generate the output files.
3. Take your own advice for updating the config template to generate the named output config file.
4. Always use strictures (use strict; use warnings; - see The strictures, according to Seuss).