If you suspect it is because of a slow march into Unicode, Try putting use bytes; at the beginning of your code. Who knows... it might work.
(some caveats apply. For example, if your perlscript file itself has a BOM or is not ascii, see perlunicode)

how about installing virtualbox for Windows, then downloading a live ISO from any modern linux, and try your data on Linux. If your program does not die, then it's a Windows only artifact. And you might want to add your findings to the bug in the hope it gets more priority/attention.

Or, find an older version of perl, and install that on a Windows machine, and test that out. Of course, you have one year, by then, hopefully, the bug is fixed.