My RVM alternative

gistfile1.rb

#!/Users/chris/.ruby/current/bin/ruby

RUBY_HOME = ENV['RUBY_HOME']

RUBIES = {:jruby => 'jruby-1.6.0', :rubinius => 'rubinius/1.2', :mri => 'mri19'}
GEM_EXECUTABLES = {:rubinius => 'gems/bin', :mri => ''}

if ARGV.empty?
  p 'Available interpreters:'
  RUBIES.each { |key,value| p key }
  exit
end

ruby = ARGV.first

update_symlinks = lambda { |ruby|
  ruby_path = RUBY_HOME + '/' + RUBIES[ruby]
  current_bin_path = RUBY_HOME + '/current/bin'
  
  executables = Dir.glob("#{ruby_path}/bin/*")

  system("rm -rf #{current_bin_path}/*")

  executables.each do |x|
    system("ln -s #{x} #{current_bin_path}/")
  end
  
  gem_bins = "#{ruby_path}/#{GEM_EXECUTABLES[ruby]}"
  gem_bin_path = RUBY_HOME + '/current/gem_bin'
  
  system("rm -rf #{gem_bin_path}")
  
  system("ln -s #{gem_bins} #{gem_bin_path}")
}