diff -Nur a/bin/multiruby b/bin/multiruby
--- a/bin/multiruby	2023-06-01 16:53:33.239069974 +0800
+++ b/bin/multiruby	2023-06-01 16:23:24.911069974 +0800
@@ -1,37 +1,24 @@
 #!/usr/bin/env ruby -w
 
-require "yaml"
+require 'multiruby'
 
-class Array
-  def human_sort
-    sort_by { |item| item.to_s.split(/(\d+)/).map { |e| [e.to_i, e] } }
-  end
-end
-
-root_dir = File.expand_path "~/.rubies"
-
-versions = Dir.chdir(root_dir) { Dir["*"] }.human_sort
+root_dir = Multiruby.root_dir
 
 def setenv dir
-  ENV["PATH"] = "#{dir}/bin:#{ENV["PATH"]}"
-end
+  bin  = "#{dir}/bin"
+  gem  = Dir["#{dir}/lib/ruby/gems/*"].first
 
-def unsetenv key
-  if ENV[key] then
-    warn "WARNING: %s is set to %p. Removing..." % [key, ENV[key]]
-    ENV.delete key
-  end
+  ENV['PATH'] = bin + File::PATH_SEPARATOR + ENV['PATH']
+  ENV['GEM_HOME'] = gem
+  ENV['GEM_PATH'] = gem
 end
 
-unsetenv "GEM_HOME"
-unsetenv "GEM_PATH"
-
 ##
-# multiruby -1 2.0 ruby_args...
+# multiruby -1 1.8.7 ruby_args...
 
 if ARGV.first == "-1" then
   ARGV.shift
-  vers = Dir["#{root_dir}/#{ARGV.shift}*"]
+  vers = Dir["#{root_dir}/install/#{ARGV.shift}*"]
 
   abort "ambiguous version: #{vers.map { |p| File.basename p }.inspect}" if
     vers.size != 1
@@ -42,24 +29,11 @@
   exec "#{dir}/bin/ruby", *ARGV
 end
 
-def maybe_load_yaml_file config
-  if config then
-    if YAML.respond_to? :safe_load_file then
-      YAML.safe_load_file config, permitted_classes: [Regexp, Symbol]
-    else
-      YAML.load_file config
-    end
-  end
-end
+versions = Multiruby.build_and_install
+versions = ENV['VERSIONS'].split(/:/) if ENV.has_key? 'VERSIONS'
 
-rcpath = File.expand_path "~/.hoerc"
-skip = if File.exist? rcpath then
-         conf = maybe_load_yaml_file rcpath
-         conf["multiruby_skip"] || []
-       end
-excl = (ENV["EXCLUDED_VERSIONS"] || "").split(/:/) + skip
-unless excl.empty? then
-  excludes = Regexp.union(*excl)
+if ENV.has_key? 'EXCLUDED_VERSIONS' then
+  excludes = Regexp.union(*ENV['EXCLUDED_VERSIONS'].split(/:/))
   versions = versions.delete_if { |v| v =~ excludes }
 end
 
@@ -68,12 +42,13 @@
 
 results = {}
 versions.each do |version|
-  dir  = "#{root_dir}/#{version}"
+  dir  = "#{root_dir}/install/#{version}"
   ruby = "#{dir}/bin/ruby"
-  ver  = version.delete_prefix "ruby-"
+
+  ruby.sub!(/bin.ruby/, 'bin/rbx') if version =~ /rubinius/
 
   puts
-  puts "VERSION = #{ver}"
+  puts "VERSION = #{version}"
   cmd = [ruby, ARGV].flatten.map { |s| s =~ /\"/ ? "'#{s}'" : s }.join(' ')
   cmd.sub!(/#{ENV['HOME']}/, '~')
   puts "CMD     = #{cmd}"
@@ -84,7 +59,7 @@
   system ruby, *ARGV
   puts
   puts "RESULT = #{$?}"
-  results[ver] = $?
+  results[version] = $?
 
   # restore the path to original state
   ENV['PATH'] = original_path
diff -Nur a/bin/multiruby_setup b/bin/multiruby_setup
--- a/bin/multiruby_setup	1970-01-01 08:00:00.000000000 +0800
+++ b/bin/multiruby_setup	2023-06-01 16:23:28.919069974 +0800
@@ -0,0 +1,74 @@
+#!/usr/bin/env ruby -w
+
+require 'multiruby'
+
+ENV.delete 'RUBYOPT'
+
+ARGV << "help" if ARGV.empty?
+
+Dir.chdir Multiruby.root_dir
+Multiruby.setup_dirs(false)
+
+ARGV.each do |spec|
+  case spec
+  when "-h", "--help", "help" then
+    Multiruby.help
+    exit 0
+  when "the_usual" then # TODO: update #help
+    ARGV.push(*Multiruby::TAGS.map { |v| "mri:tar:#{v.gsub(/_/, '.')}" })
+    ARGV << "build" << "update:rubygems"
+    system "multigem install --no-ri --no-rdoc rake minitest ZenTest gemcutter rubyforge hoe"
+  when "build" then
+    Multiruby.build_and_install
+  when "clean" then
+    Multiruby.clean
+  when "list" then
+    Multiruby.list
+  when /rm:(.*)/ then
+    Multiruby.rm $1
+  when "rubygems:merge" then
+    Multiruby.merge_rubygems
+  when "rubygems:update", "update:rubygems" then
+    Multiruby.update_rubygems
+    ARGV << "build"
+  when "update" then
+    Multiruby.update
+  when "tags" then
+    p Multiruby.tags
+  when "mri:svn:current" then
+    ARGV << "mri:svn:releases" << "mri:svn:branches" << "build"
+  when "mri:svn:releases" then
+    Multiruby::TAGS.each do |v|
+      latest = Multiruby.mri_latest_tag v
+      abort "Can't find tag #{v}" unless latest
+      ARGV << "mri:svn:tag:#{latest}:mri_rel_#{v}"
+    end
+    ARGV << "build"
+  when /mri:svn:branch:(.*)/ then
+    ver = "branches/ruby_#{$1}" unless ver == "trunk"
+    Multiruby.svn_co "#{Multiruby::MRI_SVN}/#{$1}", "mri_#{$1}"
+    ARGV << "build"
+  when "mri:svn:branches" then
+    Multiruby::BRANCHES.each do |v|
+      ARGV << "mri:svn:branch:#{v}"
+    end
+    ARGV << "build"
+  when /mri:svn:tag:(.*):(.*)/ then
+    Multiruby.svn_co "#{Multiruby::MRI_SVN}/tags/#{$1}", $2
+    ARGV << "build"
+  when /mri:svn:tag:(.*)/ then
+    ARGV << "mri:svn:tag:#{$1}:#{$1}" << "build"
+  when /mri:list:(.*)/ then
+    v   = $1
+    ver = v[/\d+\.\d+/]
+    url = "#{Multiruby::RUBY_URL}/#{ver}/"
+
+    puts Multiruby.matching_versions(url, v).join("\n")
+  when /mri:tar:(.*)/ then
+    Multiruby.fetch_tar $1
+    ARGV << "build"
+  else
+    warn "unknown spec #{spec}"
+  end
+end
+
diff -Nur a/lib/multiruby.rb b/lib/multiruby.rb
--- a/lib/multiruby.rb	1970-01-01 08:00:00.000000000 +0800
+++ b/lib/multiruby.rb	2023-06-01 16:23:33.885069974 +0800
@@ -0,0 +1,413 @@
+require 'fileutils'
+require 'open-uri'
+
+##
+# multiruby_setup is a script to help you manage multiruby.
+#
+# usage: multiruby_setup [-h|cmd|spec...]
+#
+#   cmds:
+#
+#     -h, --help, help = show this help.
+#     build            = build and install everything. used internally.
+#     clean            = clean scm build dirs and remove non-scm build dirs.
+#     list             = print installed versions.
+#     rm:$version      = remove a particular version.
+#     rubygems:merge   = symlink all rubygem dirs to one dir.
+#     tags             = list all tags from svn.
+#     update           = update svn builds.
+#     update:rubygems  = update rubygems and nuke install dirs.
+#
+#   specs:
+#
+#     the_usual              = alias for latest versions from tar + rubygems
+#     mri:svn:current        = alias for mri:svn:releases and mri:svn:branches.
+#     mri:svn:releases       = alias for supported releases of mri ruby.
+#     mri:svn:branches       = alias for active branches of mri ruby.
+#     mri:svn:branch:$branch = install a specific $branch of mri from svn.
+#     mri:svn:tag:$tag       = install a specific $tag of mri from svn.
+#     mri:tar:$version       = install a specific $version of mri from tarball.
+#
+#   environment variables:
+#
+#     GEM_URL  = url for rubygems tarballs
+#     MRI_SVN  = url for MRI SVN
+#     RUBY_URL = url for MRI tarballs
+#     VERSIONS = what versions to install
+#
+#     RUBYOPT is cleared on installs.
+#
+# NOTES:
+#
+# * you can add a symlink to your rubinius build into ~/.multiruby/install
+# * I need patches/maintainers for other implementations.
+#
+module Multiruby
+  def self.env name, fallback; ENV[name] || fallback; end # :nodoc:
+
+  TAGS     = %w(    1_8_7 1_9_1 1_9_2)
+  BRANCHES = %w(1_8 1_8_7 1_9 trunk)
+
+  VERSIONS = env('VERSIONS', TAGS.join(":").gsub(/_/, '.')).split(/:/)
+  MRI_SVN  = env 'MRI_SVN',  'http://svn.ruby-lang.org/repos/ruby'
+  RUBY_URL = env 'RUBY_URL', 'http://ftp.ruby-lang.org/pub/ruby'
+  GEM_URL  = env 'GEM_URL',  'http://files.rubyforge.vm.bytemark.co.uk/rubygems'
+
+  HELP = []
+
+  File.readlines(__FILE__).each do |line|
+    next unless line =~ /^#( |$)/
+    HELP << line.sub(/^# ?/, '')
+  end
+
+  def self.build_and_install
+    ENV.delete 'RUBYOPT'
+
+    root_dir = self.root_dir
+    versions = []
+
+    Dir.chdir root_dir do
+      self.setup_dirs
+
+      rubygems = Dir["versions/rubygems*.tgz"]
+      abort "You should delete all but one rubygem tarball" if rubygems.size > 1
+      rubygem_tarball = File.expand_path rubygems.last rescue nil
+
+      Dir.chdir "build" do
+        Dir["../versions/*"].sort.each do |tarball|
+          next if tarball =~ /rubygems/
+
+          build_dir = File.basename tarball, ".tar.gz"
+          version = build_dir.sub(/^ruby-?/, '')
+          inst_dir = "#{root_dir}/install/#{version}"
+
+          unless test ?d, inst_dir then
+            unless test ?d, build_dir then
+              if test ?d, tarball then
+                dir = File.basename tarball
+                FileUtils.ln_sf "../versions/#{dir}", "../build/#{dir}"
+              else
+                puts "creating #{inst_dir}"
+                Dir.mkdir inst_dir
+                run "tar zxf #{tarball}"
+              end
+            end
+            Dir.chdir build_dir do
+              puts "building and installing #{version}"
+              if test ?f, "configure.in" then
+                gnu_utils_build inst_dir
+              elsif test ?f, "Rakefile" then
+                rake_build inst_dir
+              else
+                raise "dunno how to build"
+              end
+
+              if rubygem_tarball and version !~ /1[._-]9|mri_trunk|rubinius/ then
+                rubygems = File.basename rubygem_tarball, ".tgz"
+                run "tar zxf #{rubygem_tarball}" unless test ?d, rubygems
+
+                Dir.chdir rubygems do
+                  run "../ruby ./setup.rb --no-rdoc --no-ri", "../log.rubygems"
+                end
+              end
+            end
+          end
+        end
+      end
+
+      versions = Dir["install/*"].map { |path| File.basename path }
+    end
+
+    versions
+  end
+
+  def self.clean
+    self.each_scm_build_dir do |style|
+      case style
+      when :svn then
+        if File.exist? "Rakefile" then
+          run "rake clean"
+        elsif File.exist? "Makefile" then
+          run "make clean"
+        end
+      else
+        FileUtils.rm_rf Dir.pwd
+      end
+    end
+  end
+
+  def self.each_scm_build_dir
+    Multiruby.in_build_dir do
+      Dir["*"].each do |dir|
+        next unless File.directory? dir
+        Dir.chdir dir do
+          if File.exist?(".svn") then
+            yield :svn
+          else
+            yield :none
+          end
+        end
+      end
+    end
+  end
+
+  def self.matching_versions url, matching=nil
+    file = URI.parse(url).read
+
+    map = {
+      "preview" => "beta",
+      "rc"      => "beta2",
+      "p"       => "release",
+      "tar"     => "aargh",
+      "gz"      => "aargh",
+    }
+
+    versions = file.scan(/href="(ruby.*tar.gz)"/).flatten.sort_by { |s|
+      s.scan(/\d+|[a-z]+/).map { |a| Integer(a) rescue map[a] || a }
+    }
+
+    versions = versions.grep(/#{Regexp.escape(matching)}/) if matching
+
+    versions
+  end
+
+  def self.fetch_tar v
+    in_versions_dir do
+      warn "  Determining latest version for #{v}"
+      ver = v[/\d+\.\d+/]
+      base = matching_versions("#{RUBY_URL}/#{ver}/", v).last
+      abort "Could not determine release for #{v}" unless base
+      url = File.join RUBY_URL, ver, base
+      unless File.file? base then
+        warn "    Fetching #{base} via HTTP... this might take a while."
+        open(url) do |f|
+          File.open base, 'w' do |out|
+            out.write f.read
+          end
+        end
+      end
+    end
+  end
+
+  def self.gnu_utils_build inst_dir
+    run "autoconf" unless test ?f, "configure"
+    run "./configure --enable-shared --prefix #{inst_dir}", "log.configure" unless
+      test ?f, "Makefile"
+    run "(nice make -j4 main; nice make main)", "log.build"
+    run "make install-nodoc", "log.install"
+  end
+
+  def self.help
+    puts HELP.join
+  end
+
+  def self.in_build_dir
+    in_root_dir "build" do
+      yield
+    end
+  end
+
+  def self.in_install_dir
+    in_root_dir "install" do
+      yield
+    end
+  end
+
+  def self.in_root_dir subdir = ""
+    Dir.chdir File.join(self.root_dir, subdir) do
+      yield
+    end
+  end
+
+  def self.in_tmp_dir
+    in_root_dir "tmp" do
+      yield
+    end
+  end
+
+  def self.in_versions_dir
+    in_root_dir "versions" do
+      yield
+    end
+  end
+
+  def self.list
+    puts "Known versions:"
+    in_install_dir do
+      Dir["*"].sort.each do |d|
+        puts "  #{d}"
+      end
+    end
+  end
+
+  def self.merge_rubygems
+    in_install_dir do
+      gems = Dir["*/lib/ruby/gems"]
+
+      unless test ?d, "../gems" then
+        FileUtils.mv gems.first, ".."
+      end
+
+      gems.each do |d|
+        FileUtils.rm_rf d
+        FileUtils.ln_sf "../../../../gems", d
+      end
+    end
+  end
+
+  def self.mri_latest_tag v
+    Multiruby.tags.grep(/#{v}/).last
+  end
+
+  def self.rake_build inst_dir
+    run "rake", "log.build"
+    FileUtils.ln_sf "../build/#{File.basename Dir.pwd}", inst_dir
+  end
+
+  def self.rm name
+    Multiruby.in_root_dir do
+      FileUtils.rm_rf Dir["*/#{name}"]
+      f = "versions/ruby-#{name}.tar.gz"
+      File.unlink f if test ?f, f
+    end
+  end
+
+  def self.root_dir
+    root_dir = File.expand_path(ENV['MULTIRUBY'] ||
+                                File.join(ENV['HOME'], ".multiruby"))
+
+    unless test ?d, root_dir then
+      puts "creating #{root_dir}"
+      Dir.mkdir root_dir, 0700
+    end
+
+    root_dir
+  end
+
+  def self.run base_cmd, log = nil
+    cmd = base_cmd
+    cmd += " > #{log} 2>&1" if log
+    puts "Running command: #{cmd}"
+    raise "ERROR: Command failed with exit code #{$?}" unless system cmd
+  end
+
+  def self.setup_dirs download = true
+    %w(build install versions tmp).each do |dir|
+      unless test ?d, dir then
+        puts "creating #{dir}"
+        Dir.mkdir dir
+        if dir == "versions" && download then
+          warn "  Downloading initial ruby tarballs to ~/.multiruby/versions:"
+          VERSIONS.each do |v|
+            self.fetch_tar v
+          end
+          warn "  ...done"
+          warn "  Put other ruby tarballs in ~/.multiruby/versions to use them."
+        end
+      end
+    end
+  end
+
+  def self.svn_co url, dir
+    Multiruby.in_versions_dir do
+      Multiruby.run "svn co #{url} #{dir}" unless File.directory? dir
+      FileUtils.ln_sf "../versions/#{dir}", "../build/#{dir}"
+    end
+  end
+
+  def self.tags
+    tags = nil
+    Multiruby.in_tmp_dir do
+      cache = "svn.tag.cache"
+      File.unlink cache if Time.now - File.mtime(cache) > 3600 rescue nil
+
+      File.open cache, "w" do |f|
+        f.write `svn ls #{MRI_SVN}/tags/`
+      end unless File.exist? cache
+
+      tags = File.read(cache).split(/\n/).grep(/^v/).reject {|s| s =~ /preview/}
+    end
+
+    tags = tags.sort_by { |t| t.scan(/\d+/).map { |s| s.to_i } }
+  end
+
+  def self.update
+    # TODO:
+    # update will look at the dir name and act accordingly rel_.* will
+    # figure out latest tag on that name and svn sw to it trunk and
+    # others will just svn update
+
+    clean = []
+
+    self.each_scm_build_dir do |style|
+      dir = File.basename(Dir.pwd)
+      warn dir
+
+      case style
+      when :svn then
+        case dir
+        when /mri_\d/ then
+          system "svn cleanup" # just in case
+          svn_up = `svn up`
+          in_build_dir do
+            if svn_up =~ /^[ADUCG] / then
+              clean << dir
+            else
+              warn "  no update"
+            end
+            FileUtils.ln_sf "../build/#{dir}", "../versions/#{dir}"
+          end
+        when /mri_rel_(.+)/ then
+          ver = $1
+          url = `svn info`[/^URL: (.*)/, 1]
+          latest = self.mri_latest_tag(ver).chomp('/')
+          new_url = File.join(File.dirname(url), latest)
+          if new_url != url then
+            run "svn sw #{new_url}"
+            clean << dir
+          else
+            warn "  no update"
+          end
+        else
+          warn "  update in this svn dir not supported yet: #{dir}"
+        end
+      else
+        warn "  update in non-svn dir not supported yet: #{dir}"
+      end
+    end
+
+    in_install_dir do
+      clean.each do |dir|
+        warn "removing install/#{dir}"
+        FileUtils.rm_rf dir
+      end
+    end
+  end
+
+  def self.update_rubygems
+    warn "  Determining latest version for rubygems"
+    html = URI.parse(GEM_URL).read
+
+    versions = html.scan(/href="rubygems-update-(\d+(?:\.\d+)+).gem/i).flatten
+    latest = versions.sort_by { |v| v.scan(/\d+/).map { |s| s.to_i } }.last
+
+    Multiruby.in_versions_dir do
+      file = "rubygems-#{latest}.tgz"
+      unless File.file? file then
+        warn "    Fetching rubygems-#{latest}.tgz via HTTP."
+        File.unlink(*Dir["rubygems*"])
+        File.open file, 'w' do |f|
+          f.write URI.parse(GEM_URL+"/"+file).read
+        end
+      end
+    end
+
+    Multiruby.in_build_dir do
+      FileUtils.rm_rf Dir["rubygems*"]
+    end
+
+    Multiruby.in_install_dir do
+      FileUtils.rm_rf Dir["*"]
+    end
+  end
+end
diff -Nur a/Manifest.txt b/Manifest.txt
--- a/Manifest.txt	2023-06-01 16:53:33.238069974 +0800
+++ b/Manifest.txt	2023-06-01 16:54:59.287069974 +0800
@@ -7,6 +7,7 @@
 articles/how_to_use_zentest.txt
 bin/multigem
 bin/multiruby
+bin/multiruby_setup
 bin/unit_diff
 bin/zentest
 example.txt
@@ -14,6 +15,7 @@
 example2.rb
 lib/focus.rb
 lib/functional_test_matrix.rb
+lib/multiruby.rb
 lib/unit_diff.rb
 lib/zentest.rb
 lib/zentest_mapping.rb