Apologies if I'm missing something obvious (I've never used Lua that much), or if I've messed it up with another mod I'm using, but for whatever reason I just can't seem to access the starting variables: rednet, greennet, output, vars. Any time I try to index in the nets or set output, there's a nil value error code, making them seem like uninitialized variable. Can you offer any guidance on what might be causing this? Thanks!

i think you were not accessing them in an event function, but on initializing the combinator.
I just released an update where you can now access all variables when initializing the combinator

That'd be it, then! Thanks so much for looking into it and making the changes.