Ruby and rake version problems

Question

$ ruby --version
ruby 1.9.2p290 (2011-07-09 revision 32553) [i686-linux
$ ls /usr/lib/ruby/
1.9.1 gems site_ruby
$ ls /usr/lib/ruby/gems/
1.9.1
Why does ruby-1.9.2 use /usr/lib/ruby/1.9.1 and /usr/lib/ruby/gems/1.9.1? Why is there no /usr/lib/ruby/1.9.2 and /usr/lib/ruby/gems/1.9.2?
$ gem list rake
*** LOCAL GEMS ***
rake (0.9.2)
$ rake --version
rake, version 0.8.7
$ /usr/lib/ruby/gems/1.9.1/gems/rake-0.9.2/bin/rake --version
rake, version 0.8.7
wtf?
How can I get rake-0.9.2 to run? I got some issues with Ruby on Rails 3.1.0.
Stupid rubygems (the package system) always seems in conflict with pacman. And no, I don't want to do an "gem update --system" because it could create even more conflicts with pacman.

Answer 1

The library paths will remain as 1.9.1 as it indicates the compatibility level (see the 1.9.2 Release Notes).
Rake 0.8.7 is installed as part of Ruby 1.9.2 however Rails 3.1 requires at least 0.9.2.
You can either:  (replaces Rake system-wide and becomes the default version)
gem install rake
or add the newer version of Rake to your Gemfile and use
bundle exec rake
in the root of your Rails app.