I really like the new 5.8 option in swift to run code directly from the command line. I noticed there is not much documentation so I wrote a post to promote this new feature and mention some interesting aspects. Hope this is helpful.
Looks like you've found a pretty glaring omissions: swift --help doesn't even mention the -e flag. Have you considered contributing an addition to that help text?
My comment about "not much documentation" was related to promotional material that this feature exists and how/when it can be useful. Also, I thought it's a good reminder that multiple statements can be used on a single line when using a semicolon as a separator.