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Given the complexity of your example system, or rather its lack of complexity, I might recommend using the “glaze” script, instead. It takes one- or two-paned systems with frits and computes a single surface that efficiently accounts for the system’s combined behavior.
Unfortunately, the glaze script is written for the C-shell, which is not commonly available under Windows. You might find a Linux machine to run it on, or install the WSL environment (Windows Subsystem for Linux) on your computer. This should also enable you to do useful things like run Radiance programs in multi-processing mode, something not well-supported under standard Windows.
These are just my suggestions. Others may have more concrete ideas on what might be going wrong with your Perl environment. This is beyond my ken, I’m afraid.
Cheers,
-Greg
P.S. I recommend using the forum search function to find posts mentioning “glaze.csh” if you want more information on this topic. See this post, for example.