[Feature]: Implement special environment variables like $?

[MrPicklePinosaur]

What would you like to see added?

[dmgolembiowski]

These are some really useful ones from different shells:

!! # Bash: Repeat the previous command but prompting with `sudo` 
$argv # fish: (self-explanatory)
$* # Bash: $argv, but as a plain ascii string slice

Personally speaking, I'd love to see the first two make a comeback. My bashrc used to have:
run() { ( $* &> /dev/null ) & } so strategically there are fair reasons to want $* as well.

Something that would be a novel shell environment variable introduction would be a lazily evaluated $. which resolves to an iterator over all (non self directory and parent directory) canonicalized file paths. This lends itself nicely to shell invocations like for file in $.; do ... done

Another curious environment variable is the $$ for the process pid. In terms of debugging custom shells, it would be nice if there existed a $SHRS environment variable that resolves to a unix domain socket path for debugging, background job management, sourcing new logins, etc.

I'd like to toy around with the idea of $ being lazily evaluated to one before the previous command.

[MrPicklePinosaur]

$SHRS as an env var is quite an interesting idea!

We are currently pretty short on dev time, but i'll keep reviewing any PRs :)