If you want to use this package as your default system ruby, as root
create symbolic links like so (overwriting any previous default):
 ln -sf /usr/local/bin/ruby18 /usr/local/bin/ruby
 ln -sf /usr/local/bin/erb18 /usr/local/bin/erb
 ln -sf /usr/local/bin/irb18 /usr/local/bin/irb
 ln -sf /usr/local/bin/rdoc18 /usr/local/bin/rdoc
 ln -sf /usr/local/bin/ri18 /usr/local/bin/ri
 ln -sf /usr/local/bin/testrb18 /usr/local/bin/testrb
