It is a simple script to define - how many words from a text file do you already know?

I want to learn English and read books, but how to define - which text is simplest to read for me? This script reads txt file with a text and counts how many distinct words it consist of. Next step - you have to mark already known words and it will be saved into a configuration file in your home directory. Unknown words will be saved into yaml file in the same folder as the original file. When you learn these words you can read and understand the text. After that you can try with other text - script will read already known words from configuration and write how many words from new text you have to learn. In this way, you can define which of new texts are simplest for your level of English. And move forward small steps ;)

Let's start with small stories and move to a great romance.