I have tried to install Ruby 1.9 from tar ball. But so far, there is a problem and it's not successful.
I borrowed the ideas from the following sites:
"Building Ruby, Rails, Subversion, Mongrel, and MySQL on Mac OS X"
"Ruby on Rails install on 10.5 OS X"
"Trouble with Readline and Building Ruby 1.9"
(Also the same post under ruby-forum: "Trouble with Readline and Building Ruby 1.9")
Still Ruby make is failing with regard to readline.
By the way, I miss Linux package managers. It was easy to see which version of what is installed. MacPort is trying to achieve the same thing. But so far, it was not successful to install it. When it comes to package management, I think Linux is better.