Programming

I can't answer your question in the title, but I can say what I do whenever I learn a new programming language (even if its temporary just to play around with new languages). My personal Hello-World like program I tackle in most cases is something that runs another program. Lot of my personal projects are actually like that. You can start simple, to learn how to do associated tasks with it. There is a lot you can learn by diving into this (first) simple exercise.

This will help you understanding how to read directories, handle file names and paths correctly, read text files in example, how to spawn a process, handle possible errors and react to error codes, possibly read and process stdout of the program. Also handle commandline options, output stdout so it can be used with other programs easily. Write configuration file and so on.

An alternative thing you can try is, doing a simple grep like program. Or maybe a simple game that asks you a few questions and gives points. Or a note taking app.