I'm not sure. I remember seeing an example in the docs, but I can't find it now. Actually the docs in general are a lot less opinionated than I remember them.
One thing that I did find is that the ion shell document mentions that it isn't a posix compliant shell because they would have had to leave out a bunch of features.
You can friend me for a code if you don't have one yet. My username is Octorine.