Exactly. If you look at the sources, you'll see that the arguments are all joined into a single string with spaces, then split back into separate words using s

Exactly. If you look at the sources, you'll see that the arguments are all joined into a single string with spaces, then split back into separate words using shlex.split(). So cat("filename with spaces in it") will fail, but cat("'filename with spaces in it') ought to succeed. It's a neat experiment, but using this module in production would not be a great idea.