Support `$pwd` for a current directory path.

[Kray-G]

The Feature

We would like to use a current directory path easily.

System.println($pwd);

Workaround

In the version 1.0.0, you can use System.cwd() for this.

System.println(System.cwd());

Additional Comment

This is a very basic functionality.
So I will port it back also to v1.0.x.