I was talking about the size of the file in the archive, not the size of the output.

For example, add:
10000000  DeflatN  83362  89%  04-04-05  19:00  8e76dc22   file2.dat
or
 704106  DeflatN  4      100%  04-04-05  19:00  8e76dc22   file3.dat
to your __DATA__ and you'll notice an extra space in front of the file name. Now, I'm not sure how his unzip program handles these cases, so substr may actually work.