The first thing that I did with Perl which resulted in my learning a lot of it was I wrote a program that was an endless loop. Every time it read a line it would copy the clipboard into $_, do something, and copy $_ back to the clipboard. (Using Win32::Clipboard of course.)

The "do something" could be standard reformatting, copy, run some code, whatever. The script was awful in design and execution. However by always reaching for this (while working in VB without a decent editor) I learned regular expressions, had somewhere to play around with snippets of code meaning that I learned more, and it helped me get work done.

In fact I still use the darned thing...