Ok, if it works on Windows there is something else causing the problem.
Specifically what I'm trying to do is run a separate murgaLua process that runs a new script using a variable created in the current script. This is what I have working in Linux:

MURGALUA is the murgaLua executable
tempfile is a dynamically created script file
images is a Lua variable being passed, which is a directory that tempfile wouldn't be able to find otherwise.
If I recall correctly, I got a "bad symbol" error in Windows.

This also works in Linux, but I haven't yet tested in Windows:

Maybe there is a problem with the string being interpreted first for io.popen and then being misinterpreted when it's run. It might end up being sent in this format:

If that's the case, I think it might be a problem with using a backslash escape after all.
It looks like one option could be something like this:

which I hope would run this command:

However, I could see it doing this instead:

which I guess would probably also fail.

Perhaps the best solution would be

which is essentially the same as the second one above but with the single and double quotes swapped, hopefully resulting in this:

That one looks like it should work in Windows.