i need a module for more involved command line parsing

[snippsat]

line 11 is @click.argument('arg', nargs=-1). where do those 2 "arguments" go?

All is good document in Click Variadic Arguments .

This can be controlled with the nargs parameter. If it is set to -1, then an unlimited number of arguments is accepted.

telling me that a decorator does make changes is not telling me how i could make use of the feature in my own programming

If want to learn decorate then use tutorial/books it's a lot written about it,it's not the goal of Click to learn user decorator.
This is the goal,decorator help with "as little code as necessary" for users.

Click is a Python package for creating beautiful command line interfaces in a composable way with as little code as necessary

do you know how to write a decorator function?

Did write one one in post #5,just as an easy example to understand.
Also if write a more robust version that meant to be used be other would also used @functools.wraps.
Or better wrapt.
This so metadata/signature of function eg __module__, __name__, __qualname__, __doc__, and __annotations__,don't get lost.

I am finish with this Thread now ,the whole point was in post #2 to give a advice that i think Click is okay for these tasks.