Pik & RVM, tools to manage multiple Ruby versions on Windows, OS X, Linux

I have a Rails application that I have upgraded from Rails 2.3.5 to Rails 3.0.3. Removed deprecations and made that application stable on Rails 3.0.3. And now, it was Ruby turn to be upgraded from
 - Ruby 1.8.7 to Ruby 1.9.2.

This Ruby Migration was really going to be a challenging one because of two reasons:
Firstly, My application is running on Windows as well as on Linux, Ubuntu, Mac.
Secondly, I need both Ruby versions, 1.8.7 and 1.9.2 for my application because I don't know how my application will behave with Ruby 1.9.2, what are the things that will break, so be on safer side  I want both versions.

My basic requirement was to be able to switch between Ruby versions easily so that rest of my work doesn't get impacted because of Ruby upgradation. I have heard of RVM (Ruby Version Manager) that makes it easy to install and switch between multiple Ruby versions on OS X and Linux.

But, sadly RVM cannot be used on Windows. Now what! To my rescue, came another gud tool, Pik.

Pik is a tool to manage multiple versions of ruby on Windows. It can be used from the Windows command line (cmd.exe), Windows PowerShell, or Git Bash. Very much similar to RVM.

In next few blogs, watch how to install Pik, upgrade Ruby version to 1.9.2 on Windows and challenges faced during upgradation.