$ dpkg --get-selections | grep ruby
libdbm-ruby1.9.1                                install
libgdbm-ruby1.9.1                               install
libopenssl-ruby1.9.1                            install
libreadline-ruby1.9.1                           install
libruby1.8                                      install
libruby1.9.1                                    install
libruby1.9.1-dbg                                install
libtcltk-ruby1.9.1                              install
ruby1.8                                         install
ruby1.9.1                                       install
ruby1.9.1-dev                                   install
ruby1.9.1-examples                              install
ruby1.9.1-full                                  install
rubygems                                        deinstall
rubygems1.8                                     install