Build a trivial program

So I thought of a reasonably trivial program I could write which would still be interesting enough and which can be build upon for a while to build some skill in perl GUI programming.
I think it would be nice to be able to build a GUI for linux command line programs, that could have some value in the future. As that could quickly become to complex for my purpose and it would probably drive me to start messing with the code for the utility I want to write a GUI for, I chose instead to start writing a GUI for native built in shell commands. I know this is not the most useful thing to do, but still it may become an interesting learning tool