Now that Microsoft is making .NET Core and PowerShell Core available
on Linux and Mac, would someone who does recreational programming on
one of those two OSes please see if you can find a language spec for
it, and also information regarding what .NET Core doesn't support
that's in the full .NET framework for Windows?

I am given to understand that it claims to be an alpha of version 6,
and the full release on Windows is currently version 5.1, so if I
start writing Traveller by the Byte in PowerShell 5 (as I am
considering; I've gotten feedback that says that APL is just too
opaque as a language, and I'm finding that it doesn't handle data
structures at all well), it should work on the Linux and MacOS
releases - but I also need to know what to avoid using.

Also, some opinion/debate, please: As a cross-platform data
storage/data transfer format: XML or JSON?