installing ruby 1.9.1 is very easy .......
follow simple steps

wget ftp://ftp.ruby-lang.org/pub/ruby/1.9/ruby-1.9.1-p0.tar.gz

tar -xvf ruby-1.9.1-p0.tar.gz

cd ruby-1.9.1-p0
./configure

make
make test
sudo make install


Thats, it !