install_package "yaml-0.1.6" "http://pyyaml.org/download/libyaml/yaml-0.1.6.tar.gz#7da6971b4bd08a986dd2a61353bc422362bd0edcc67d7ebaac68c95f74182749" --if needs_yaml
install_package "openssl-1.0.1h" "https://www.openssl.org/source/openssl-1.0.1h.tar.gz#9d1c8a9836aa63e2c6adb684186cbd4371c9e9dcc01d6e3bb447abf2d4d3d093" mac_openssl --if has_broken_mac_openssl
install_package "ruby-2.0.0-preview2" "http://cache.ruby-lang.org/pub/ruby/2.0/ruby-2.0.0-preview2.tar.gz#03d15c7c643f737906c7736820bf4d6f3a71aa8f1dce343284240fee5665f970" standard verify_openssl