Maybe we didn't give you a crystal clear reply. First, the program should run using the data segment. Then take the data after __DATA__ and put that into "somefile". In the program, you need to add at the beginning,

open FILE, '<', "somefile" or die "unable to open file $!";
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Now put FILE everywhere that DATA appears in the program. You will now be reading "somefile" on the disk instead of the __DATA__ section.