Where X = Programming language that you want to learn & Y = Programming language that you already know.
Lean X if you know Y is a different way to learn the syntax of a new programming language if you already know other. Just select the language that you want to learn and the language that you already know. Now you can start to learn with comparative examples about coding different stuff in each language.
Just go to Learn X if you know Y, choose the desired languages, and start to learn. It's a piece of cake.
This site needs help to grow. If you know some programming language (it doesn't matter if we already have it in the site or not), and want to help us, go to contributing.md and read the instruction for making contributions.
Project repository is under the MIT license. Site content is shared under a CC BY-NC-SA 3.0 license.