Module: Bash like shell written in vibe
Short: psh

This is the top level module for a program that is an interactive user shell.  The shell
is loosely based on bash, so command line syntax such as ; & > < 2>&1 etc should be
supported.  The shell should have sophisticated command line editing, similar to bash with
the ability to quickly move forward and backward in the command line.  Commonly used
commands such as the up-arrow for command line history, the history command, and the
ability to ! execute a prior command should be supported.  The shell should support tab
expansion.  The shell should support ~.

The shell should support
environment variables, but with a syntax for setting and accessing them similar to Python.  These
environment variables should all be stored in a single dictionary, inside 
the program.  Call this dictionary "env".

The shell should support an environment variable "prompt" that holds a string that is
the prompt presented to the user.  The default prompt should be "$ ".

The shell should support a "path" variable that holds a set of directories that should
be searched when trying to execute a command or tab complete.  The default path
should either be copied from the system environment PATH or path variable or if none
exists, be set to "/bin:/usr/bin:/usr/sbin:.".

The shell will not execute the bash scripting language, instead Python will be the core scripting language.  When a python file is asked for execution that Python code should be
executed by an external Python process.  When Python code is written inline on the command line, it
should be executed within the shell program itself.  This inline code should be written
inside parenthesis.  When it can be described in one line then it can be written inline.  For example: (env["x"] = 1)  If more than one line is required, the \ should be used to 
create it.  For example:

(\
env["x"] = env["x"] + 1\
if env["x"] == 10:\
    print(env["x"])\
)

This code is executed after the \ chars are removed.

Internally executed code should be guarded with exception
handling so it does not crash the shell.  This internally executed code can access and change
environment variables.  Python files on disk can be executed internally as well if the command
"source" is prefixed in front of the filename.

A command "help" should be provided that details how to use the shell.