Adding comma to interpolated regex so they can be used in concats

Fixes #696 

I don't think the regex is sustainable or at the very least, we need to come up with a list of valid characters that can be used within an interpolation. Since we now have `concat`, basically the user can input any string values which we continually come up against this regex.

So for now, I've just added the comma to to regex valid chars to fix my own case.