Install ruby 1.9.3-p327-perf without the ruby-build listing (by patching existing ruby) - save this file in /tmp/ and run with rbenv install /tmp/1.9.3-p327-perf

1.9.3-p327-perf

build_package_combined_patch() {
  local package_name="$1"
 
  {
    curl https://gist.github.com/funny-falcon/4136373/raw/0b65118d0e0930c5dc15479722309fac971af902/falcon-gc.diff | patch -p1
    autoconf
    ./configure --prefix="$PREFIX_PATH" $CONFIGURE_OPTS
    make -j 8
    make install
  } >&4 2>&1
 
}
 
install_package "yaml-0.1.4" "http://pyyaml.org/download/libyaml/yaml-0.1.4.tar.gz"
install_package "ruby-1.9.3-p327" "http://ftp.ruby-lang.org/pub/ruby/1.9/ruby-1.9.3-p327.tar.gz" combined_patch

As m-shirshendu commented here: https://gist.github.com/burke/1688857

To get rid of the following error:

regparse.c:582:15: error: implicit conversion loses integer precision: 'st_index_t' (aka 'unsigned long') to 'int' [-Werror,-Wshorten-64-to-32]
In addition to https://gist.github.com/umtrey/7592062, I had to do the following first

brew update
brew tap homebrew/dupes
brew install apple-gcc42
export CC=gcc-4.2

Then rbenv install /tmp/1.9.3-p327-perf