diff --git a/.github/actions/package/action.yml b/.github/actions/package/action.yml
new file mode 100644
index 0000000..bc0a2cd
--- /dev/null
+++ b/.github/actions/package/action.yml
@@ -0,0 +1,62 @@
+name: Upload built package
+description: >-
+  Build and update package.
+
+inputs:
+  upload-files:
+    required: false
+    default: 'pkg/*.gem'
+    description: File name pattern to upload.
+
+  package-name:
+    required: false
+    default: '${GITHUB_REPOSITORY#*/}-${RUNNER_OS%-*}'
+    description: Package name to upload.
+
+  build-program:
+    required: false
+    default: rake build
+    description: Command to build package files.
+
+runs:
+  using: composite
+
+  steps:
+    - id: setup
+      run: |
+        : Setup
+        PS4="##[command]"; set -x
+        : Fetch deeper for changelogs
+        git fetch --force --no-tags origin 'refs/tags/v*:refs/tags/v*'
+        set -- "$(git symbolic-ref --short HEAD)" $(git tag --list --no-contains HEAD --sort -version:refname)
+        branch=$1 prev=$2
+        git fetch ${prev:+--shallow-exclude=}${prev:---unshallow} origin ${branch}
+        : Re-checkout with LF
+        git config core.autocrlf false
+        git config core.eol lf
+        git checkout -f
+      shell: bash
+
+    - id: build
+      run: |
+        : Build
+        if command -v shasum > /dev/null; then
+          shasum=(shasum -a 256 -b) # Ubuntu, macOS
+        elif command -v sha256sum > /dev/null; then
+          shasum=(sha256sum -b) # Windows
+        else                    # fallback
+          shasum=(ruby -rdigest -e "ARGV.each{|f| print Digest::SHA256.file(f).hexdigest, ' *'; puts f}")
+        fi
+        PS4="##[command]"; set -x
+        ${{ inputs.build-program }}
+        : Show info
+        ls -l ${{ inputs.upload-files }}
+        "${shasum[@]}" ${{ inputs.upload-files }}
+        echo pkg="${{ inputs.package-name }}" >> $GITHUB_OUTPUT
+      shell: bash
+
+    - id: upload
+      uses: actions/upload-artifact@v4
+      with:
+        path: ${{ inputs.upload-files }}
+        name: ${{ steps.build.outputs.pkg }}
diff --git a/.github/workflows/codeql.yml b/.github/workflows/codeql.yml
new file mode 100644
index 0000000..ee28f6b
--- /dev/null
+++ b/.github/workflows/codeql.yml
@@ -0,0 +1,84 @@
+# For most projects, this workflow file will not need changing; you simply need
+# to commit it to your repository.
+#
+# You may wish to alter this file to override the set of languages analyzed,
+# or to provide custom queries or build logic.
+#
+# ******** NOTE ********
+# We have attempted to detect the languages in your repository. Please check
+# the `language` matrix defined below to confirm you have the correct set of
+# supported CodeQL languages.
+#
+name: "CodeQL"
+
+on:
+  push:
+    branches: [ "master" ]
+  pull_request:
+    branches: [ "master" ]
+  schedule:
+    - cron: '35 1 * * 0'
+
+jobs:
+  analyze:
+    name: Analyze
+    # Runner size impacts CodeQL analysis time. To learn more, please see:
+    #   - https://gh.io/recommended-hardware-resources-for-running-codeql
+    #   - https://gh.io/supported-runners-and-hardware-resources
+    #   - https://gh.io/using-larger-runners
+    # Consider using larger runners for possible analysis time improvements.
+    runs-on: ${{ (matrix.language == 'swift' && 'macos-latest') || 'ubuntu-latest' }}
+    timeout-minutes: ${{ (matrix.language == 'swift' && 120) || 360 }}
+    permissions:
+      # required for all workflows
+      security-events: write
+
+      # only required for workflows in private repositories
+      actions: read
+      contents: read
+
+    strategy:
+      fail-fast: false
+      matrix:
+        language: [ 'ruby' ]
+        # CodeQL supports [ 'c-cpp', 'csharp', 'go', 'java-kotlin', 'javascript-typescript', 'python', 'ruby', 'swift' ]
+        # Use only 'java-kotlin' to analyze code written in Java, Kotlin or both
+        # Use only 'javascript-typescript' to analyze code written in JavaScript, TypeScript or both
+        # Learn more about CodeQL language support at https://aka.ms/codeql-docs/language-support
+
+    steps:
+    - name: Checkout repository
+      uses: actions/checkout@v4
+
+    # Initializes the CodeQL tools for scanning.
+    - name: Initialize CodeQL
+      uses: github/codeql-action/init@v3
+      with:
+        languages: ${{ matrix.language }}
+        # If you wish to specify custom queries, you can do so here or in a config file.
+        # By default, queries listed here will override any specified in a config file.
+        # Prefix the list here with "+" to use these queries and those in the config file.
+
+        # For more details on CodeQL's query packs, refer to: https://docs.github.com/en/code-security/code-scanning/automatically-scanning-your-code-for-vulnerabilities-and-errors/configuring-code-scanning#using-queries-in-ql-packs
+        # queries: security-extended,security-and-quality
+
+
+    # Autobuild attempts to build any compiled languages (C/C++, C#, Go, Java, or Swift).
+    # If this step fails, then you should remove it and run the build manually (see below)
+    - name: Autobuild
+      uses: github/codeql-action/autobuild@v3
+
+    # ℹ️ Command-line programs to run using the OS shell.
+    # 📚 See https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#jobsjob_idstepsrun
+
+    #   If the Autobuild fails above, remove it and uncomment the following three lines.
+    #   modify them (or add more) to build your code if your project, please refer to the EXAMPLE below for guidance.
+
+    # - run: |
+    #     echo "Run, Build Application using script"
+    #     ./location_of_script_within_repo/buildscript.sh
+
+    - name: Perform CodeQL Analysis
+      uses: github/codeql-action/analyze@v3
+      with:
+        category: "/language:${{matrix.language}}"
diff --git a/.github/workflows/push_gem.yml b/.github/workflows/push_gem.yml
new file mode 100644
index 0000000..4e02df3
--- /dev/null
+++ b/.github/workflows/push_gem.yml
@@ -0,0 +1,46 @@
+name: Publish gem to rubygems.org
+
+on:
+  push:
+    tags:
+      - 'v*'
+
+permissions:
+  contents: read
+
+jobs:
+  push:
+    if: github.repository == 'ruby/optparse'
+    runs-on: ubuntu-latest
+
+    environment:
+      name: rubygems.org
+      url: https://rubygems.org/gems/optparse
+
+    permissions:
+      contents: write
+      id-token: write
+
+    steps:
+      - name: Harden Runner
+        uses: step-security/harden-runner@0634a2670c59f64b4a01f0f96f84700a4088b9f0 # v2.12.0
+        with:
+          egress-policy: audit
+
+      - uses: actions/checkout@0ad4b8fadaa221de15dcec353f45205ec38ea70b # v4.1.4
+
+      - name: Set up Ruby
+        uses: ruby/setup-ruby@a6e6f86333f0a2523ece813039b8b4be04560854 # v1.190.0
+        with:
+          bundler-cache: true
+          ruby-version: ruby
+
+      - name: Publish to RubyGems
+        uses: rubygems/release-gem@a25424ba2ba8b387abc8ef40807c2c85b96cbe32 # v1.1.1
+
+      - name: Create GitHub release
+        run: |
+          tag_name="$(git describe --tags --abbrev=0)"
+          gh release create "${tag_name}" --verify-tag --generate-notes
+        env:
+          GITHUB_TOKEN: ${{ secrets.MATZBOT_GITHUB_WORKFLOW_TOKEN }}
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 0c2decb..2736e12 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -21,17 +21,13 @@ jobs:
         ruby: ${{ fromJson(needs.ruby-versions.outputs.versions) }}
         os: [ ubuntu-latest, macos-latest, windows-latest ]
         exclude:
+          - { os: macos-latest, ruby: 2.5 }
           - { os: windows-latest, ruby: truffleruby-head }
           - { os: windows-latest, ruby: truffleruby }
           - { os: windows-latest, ruby: jruby-head }
           - { os: windows-latest, ruby: jruby }
     runs-on: ${{ matrix.os }}
     steps:
-    - name: git config
-      run: |
-        git config --global core.autocrlf false
-        git config --global core.eol lf
-        git config --global advice.detachedHead 0
     - uses: actions/checkout@v4
     - name: Set up Ruby
       uses: ruby/setup-ruby@v1
@@ -42,19 +38,5 @@ jobs:
     - name: Run test
       run: rake test
 
-    - id: build
-      run: |
-        rake build
-        ls -l pkg/*.gem
-        shasum -a 256 pkg/*.gem
-        echo "pkg=${GITHUB_REPOSITORY#*/}-${RUNNING_OS%-*}" >> $GITHUB_OUTPUT
-      env:
-        RUNNING_OS: ${{matrix.os}}
-      shell: bash
-      if: ${{ matrix.os != 'windows-latest' }}
-    - name: Upload package
-      uses: actions/upload-artifact@v3
-      with:
-        path: pkg/*.gem
-        name: ${{steps.build.outputs.pkg}}
-      if: ${{ steps.build.outcome == 'success' }}
+    - uses: ./.github/actions/package
+      if: ${{ matrix.ruby == needs.ruby-versions.outputs.latest }}
diff --git a/.rdoc_options b/.rdoc_options
index 79a8fce..24fe2d7 100644
--- a/.rdoc_options
+++ b/.rdoc_options
@@ -2,3 +2,4 @@
 page_dir: doc
 main_page: README.md
 title: Documentation for OptionParser
+op_dir: rdoc
diff --git a/BSDL b/BSDL
new file mode 100644
index 0000000..66d9359
--- /dev/null
+++ b/BSDL
@@ -0,0 +1,22 @@
+Copyright (C) 1993-2013 Yukihiro Matsumoto. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions
+are met:
+1. Redistributions of source code must retain the above copyright
+   notice, this list of conditions and the following disclaimer.
+2. Redistributions in binary form must reproduce the above copyright
+   notice, this list of conditions and the following disclaimer in the
+   documentation and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+SUCH DAMAGE.
diff --git a/README.md b/README.md
index 67d829f..160a4e7 100644
--- a/README.md
+++ b/README.md
@@ -50,7 +50,7 @@ p ARGV
 
 ## Development
 
-After checking out the repo, run `bin/setup` to install dependencies. Then, run `rake test` to run the tests. You can also run `bin/console` for an interactive prompt that will allow you to experiment.
+After checking out the repo, run `bundle install` to install dependencies. Then, run `rake test` to run the tests.
 
 To install this gem onto your local machine, run `bundle exec rake install`. To release a new version, update the version number in `version.rb`, and then run `bundle exec rake release`, which will create a git tag for the version, push git commits and tags, and push the `.gem` file to [rubygems.org](https://rubygems.org).
 
diff --git a/doc/optparse/argument_converters.rdoc b/doc/optparse/argument_converters.rdoc
index 4b4b30e..5327298 100644
--- a/doc/optparse/argument_converters.rdoc
+++ b/doc/optparse/argument_converters.rdoc
@@ -377,4 +377,4 @@ Executions:
   $ ruby match_converter.rb --capitalize foo
   ["Foo", String]
   $ ruby match_converter.rb --capitalize "foo bar"
-  match_converter.rb:9:in `<main>': invalid argument: --capitalize foo bar (OptionParser::InvalidArgument)
+  match_converter.rb:9:in '<main>': invalid argument: --capitalize foo bar (OptionParser::InvalidArgument)
diff --git a/doc/optparse/option_params.rdoc b/doc/optparse/option_params.rdoc
index 55f9b53..575ee66 100644
--- a/doc/optparse/option_params.rdoc
+++ b/doc/optparse/option_params.rdoc
@@ -31,7 +31,7 @@ Contents:
     - {Long Names with Optional Arguments}[#label-Long+Names+with+Optional+Arguments]
     - {Long Names with Negation}[#label-Long+Names+with+Negation]
   - {Mixed Names}[#label-Mixed+Names]
-- {Argument Styles}[#label-Argument+Styles]
+- {Argument Strings}[#label-Argument+Strings]
 - {Argument Values}[#label-Argument+Values]
   - {Explicit Argument Values}[#label-Explicit+Argument+Values]
     - {Explicit Values in Array}[#label-Explicit+Values+in+Array]
@@ -91,7 +91,7 @@ Executions:
   Usage: short_required [options]
       -xXXX                            Short name with required argument
   $ ruby short_required.rb -x
-  short_required.rb:6:in `<main>': missing argument: -x (OptionParser::MissingArgument)
+  short_required.rb:6:in '<main>': missing argument: -x (OptionParser::MissingArgument)
   $ ruby short_required.rb -x FOO
   ["-x", "FOO"]
 
@@ -181,7 +181,7 @@ Executions:
   Usage: long_required [options]
           --xxx XXX                    Long name with required argument
   $ ruby long_required.rb --xxx
-  long_required.rb:6:in `<main>': missing argument: --xxx (OptionParser::MissingArgument)
+  long_required.rb:6:in '<main>': missing argument: --xxx (OptionParser::MissingArgument)
   $ ruby long_required.rb --xxx FOO
   ["--xxx", "FOO"]
 
@@ -243,11 +243,11 @@ Usage: mixed_names [options]
   $ ruby mixed_names.rb --xxx
   ["--xxx", true]
   $ ruby mixed_names.rb -y
-  mixed_names.rb:12:in `<main>': missing argument: -y (OptionParser::MissingArgument)
+  mixed_names.rb:12:in '<main>': missing argument: -y (OptionParser::MissingArgument)
   $ ruby mixed_names.rb -y FOO
   ["--yyy", "FOO"]
   $ ruby mixed_names.rb --yyy
-  mixed_names.rb:12:in `<main>': missing argument: --yyy (OptionParser::MissingArgument)
+  mixed_names.rb:12:in '<main>': missing argument: --yyy (OptionParser::MissingArgument)
   $ ruby mixed_names.rb --yyy BAR
   ["--yyy", "BAR"]
   $ ruby mixed_names.rb -z
@@ -279,7 +279,7 @@ Executions:
   Usage: argument_keywords [options]
       -x, --xxx                        Required argument
   $ ruby argument_styles.rb --xxx
-  argument_styles.rb:6:in `<main>': missing argument: --xxx (OptionParser::MissingArgument)
+  argument_styles.rb:6:in '<main>': missing argument: --xxx (OptionParser::MissingArgument)
   $ ruby argument_styles.rb --xxx FOO
   ["--xxx", "FOO"]
 
@@ -298,7 +298,7 @@ Executions:
   Usage: argument_strings [options]
       -x, --xxx=XXX                    Required argument
   $ ruby argument_strings.rb --xxx
-  argument_strings.rb:9:in `<main>': missing argument: --xxx (OptionParser::MissingArgument)
+  argument_strings.rb:9:in '<main>': missing argument: --xxx (OptionParser::MissingArgument)
   $ ruby argument_strings.rb --xxx FOO
   ["--xxx", "FOO"]
 
@@ -331,7 +331,7 @@ Executions:
       -xXXX                            Values for required argument
       -y [YYY]                         Values for optional argument
   $ ruby explicit_array_values.rb -x
-  explicit_array_values.rb:9:in `<main>': missing argument: -x (OptionParser::MissingArgument)
+  explicit_array_values.rb:9:in '<main>': missing argument: -x (OptionParser::MissingArgument)
   $ ruby explicit_array_values.rb -x foo
   ["-x", "foo"]
   $ ruby explicit_array_values.rb -x f
@@ -339,9 +339,9 @@ Executions:
   $ ruby explicit_array_values.rb -x bar
   ["-x", "bar"]
   $ ruby explicit_array_values.rb -y ba
-  explicit_array_values.rb:9:in `<main>': ambiguous argument: -y ba (OptionParser::AmbiguousArgument)
+  explicit_array_values.rb:9:in '<main>': ambiguous argument: -y ba (OptionParser::AmbiguousArgument)
   $ ruby explicit_array_values.rb -x baz
-  explicit_array_values.rb:9:in `<main>': invalid argument: -x baz (OptionParser::InvalidArgument)
+  explicit_array_values.rb:9:in '<main>': invalid argument: -x baz (OptionParser::InvalidArgument)
 
 
 ===== Explicit Values in Hash
@@ -361,7 +361,7 @@ Executions:
       -xXXX                            Values for required argument
       -y [YYY]                         Values for optional argument
   $ ruby explicit_hash_values.rb -x
-  explicit_hash_values.rb:9:in `<main>': missing argument: -x (OptionParser::MissingArgument)
+  explicit_hash_values.rb:9:in '<main>': missing argument: -x (OptionParser::MissingArgument)
   $ ruby explicit_hash_values.rb -x foo
   ["-x", 0]
   $ ruby explicit_hash_values.rb -x f
@@ -369,7 +369,7 @@ Executions:
   $ ruby explicit_hash_values.rb -x bar
   ["-x", 1]
   $ ruby explicit_hash_values.rb -x baz
-  explicit_hash_values.rb:9:in `<main>': invalid argument: -x baz (OptionParser::InvalidArgument)
+  explicit_hash_values.rb:9:in '<main>': invalid argument: -x baz (OptionParser::InvalidArgument)
   $ ruby explicit_hash_values.rb -y
   ["-y", nil]
   $ ruby explicit_hash_values.rb -y baz
@@ -377,14 +377,15 @@ Executions:
   $ ruby explicit_hash_values.rb -y bat
   ["-y", 3]
   $ ruby explicit_hash_values.rb -y ba
-  explicit_hash_values.rb:9:in `<main>': ambiguous argument: -y ba (OptionParser::AmbiguousArgument)
+  explicit_hash_values.rb:9:in '<main>': ambiguous argument: -y ba (OptionParser::AmbiguousArgument)
   $ ruby explicit_hash_values.rb -y bam
   ["-y", nil]
 
 ==== Argument Value Patterns
 
 You can restrict permissible argument values
-by specifying a Regexp that the given argument must match.
+by specifying a +Regexp+ that the given argument must match,
+or a +Range+ or +Array+ that the converted value must be included in.
 
 File +matched_values.rb+ defines options with matched argument values.
 
@@ -395,12 +396,22 @@ Executions:
   $ ruby matched_values.rb --help
   Usage: matched_values [options]
           --xxx XXX                    Matched values
+          --yyy YYY                    Check by range
+          --zzz ZZZ                    Check by list
   $ ruby matched_values.rb --xxx foo
   ["--xxx", "foo"]
   $ ruby matched_values.rb --xxx FOO
   ["--xxx", "FOO"]
   $ ruby matched_values.rb --xxx bar
-  matched_values.rb:6:in `<main>': invalid argument: --xxx bar (OptionParser::InvalidArgument)
+  matched_values.rb:12:in '<main>': invalid argument: --xxx bar (OptionParser::InvalidArgument)
+  $ ruby matched_values.rb --yyy 1
+  ["--yyy", 1]
+  $ ruby matched_values.rb --yyy 4
+  matched_values.rb:12:in '<main>': invalid argument: --yyy 4 (OptionParser::InvalidArgument)
+  $ ruby matched_values.rb --zzz 1
+  ["--zzz", 1]
+  $ ruby matched_values.rb --zzz 2
+  matched_values.rb:12:in '<main>': invalid argument: --zzz 2 (OptionParser::InvalidArgument)
 
 === Argument Converters
 
diff --git a/doc/optparse/ruby/argument_abbreviation.rb b/doc/optparse/ruby/argument_abbreviation.rb
new file mode 100644
index 0000000..49007eb
--- /dev/null
+++ b/doc/optparse/ruby/argument_abbreviation.rb
@@ -0,0 +1,9 @@
+require 'optparse'
+parser = OptionParser.new
+parser.on('-x', '--xxx=VALUE', %w[ABC def], 'Argument abbreviations') do |value|
+  p ['--xxx', value]
+end
+parser.on('-y', '--yyy=VALUE', {"abc"=>"XYZ", def: "FOO"}, 'Argument abbreviations') do |value|
+  p ['--yyy', value]
+end
+parser.parse!
diff --git a/doc/optparse/ruby/matched_values.rb b/doc/optparse/ruby/matched_values.rb
index f184ca8..a1aba14 100644
--- a/doc/optparse/ruby/matched_values.rb
+++ b/doc/optparse/ruby/matched_values.rb
@@ -3,4 +3,10 @@
 parser.on('--xxx XXX', /foo/i, 'Matched values') do |value|
   p ['--xxx', value]
 end
+parser.on('--yyy YYY', Integer, 'Check by range', 1..3) do |value|
+  p ['--yyy', value]
+end
+parser.on('--zzz ZZZ', Integer, 'Check by list', [1, 3, 4]) do |value|
+  p ['--zzz', value]
+end
 parser.parse!
diff --git a/doc/optparse/tutorial.rdoc b/doc/optparse/tutorial.rdoc
index b104379..1134f94 100644
--- a/doc/optparse/tutorial.rdoc
+++ b/doc/optparse/tutorial.rdoc
@@ -111,7 +111,7 @@ Executions:
   ["x", true]
   ["input_file.txt", "output_file.txt"]
   $ ruby basic.rb -a
-  basic.rb:16:in `<main>': invalid option: -a (OptionParser::InvalidOption)
+  basic.rb:16:in '<main>': invalid option: -a (OptionParser::InvalidOption)
 
 === Defining Options
 
@@ -232,11 +232,11 @@ Executions:
   $ ruby mixed_names.rb --xxx
   ["--xxx", true]
   $ ruby mixed_names.rb -y
-  mixed_names.rb:12:in `<main>': missing argument: -y (OptionParser::MissingArgument)
+  mixed_names.rb:12:in '<main>': missing argument: -y (OptionParser::MissingArgument)
   $ ruby mixed_names.rb -y FOO
   ["--yyy", "FOO"]
   $ ruby mixed_names.rb --yyy
-  mixed_names.rb:12:in `<main>': missing argument: --yyy (OptionParser::MissingArgument)
+  mixed_names.rb:12:in '<main>': missing argument: --yyy (OptionParser::MissingArgument)
   $ ruby mixed_names.rb --yyy BAR
   ["--yyy", "BAR"]
   $ ruby mixed_names.rb -z
@@ -270,9 +270,9 @@ Executions:
   $ ruby name_abbrev.rb --draft
   ["--draft", true]
   $ ruby name_abbrev.rb --d
-  name_abbrev.rb:9:in `<main>': ambiguous option: --d (OptionParser::AmbiguousOption)
+  name_abbrev.rb:9:in '<main>': ambiguous option: --d (OptionParser::AmbiguousOption)
   $ ruby name_abbrev.rb --dr
-  name_abbrev.rb:9:in `<main>': ambiguous option: --dr (OptionParser::AmbiguousOption)
+  name_abbrev.rb:9:in '<main>': ambiguous option: --dr (OptionParser::AmbiguousOption)
   $ ruby name_abbrev.rb --dry
   ["--dry-run", true]
   $ ruby name_abbrev.rb --dra
@@ -285,7 +285,7 @@ You can disable abbreviation using method +require_exact+.
 Executions:
 
   $ ruby no_abbreviation.rb --dry-ru
-  no_abbreviation.rb:10:in `<main>': invalid option: --dry-ru (OptionParser::InvalidOption)
+  no_abbreviation.rb:10:in '<main>': invalid option: --dry-ru (OptionParser::InvalidOption)
   $ ruby no_abbreviation.rb --dry-run
   ["--dry-run", true]
 
@@ -323,7 +323,7 @@ Executions:
 Omitting a required argument raises an error:
 
   $ ruby required_argument.rb -x
-  required_argument.rb:9:in `<main>': missing argument: -x (OptionParser::MissingArgument)
+  required_argument.rb:9:in '<main>': missing argument: -x (OptionParser::MissingArgument)
 
 ==== Option with Optional Argument
 
@@ -351,6 +351,29 @@ Executions:
 
 Omitting an optional argument does not raise an error.
 
+==== Argument Abbreviations
+
+Specify an argument list as an Array or a Hash.
+
+  :include: ruby/argument_abbreviation.rb
+
+When an argument is abbreviated, the expanded argument yielded.
+
+Executions:
+
+  $ ruby argument_abbreviation.rb --help
+  Usage: argument_abbreviation [options]
+  Usage: argument_abbreviation [options]
+      -x, --xxx=VALUE                  Argument abbreviations
+      -y, --yyy=VALUE                  Argument abbreviations
+  $ ruby argument_abbreviation.rb --xxx A
+  ["--xxx", "ABC"]
+  $ ruby argument_abbreviation.rb --xxx c
+  argument_abbreviation.rb:9:in '<main>': invalid argument: --xxx c (OptionParser::InvalidArgument)
+  $ ruby argument_abbreviation.rb --yyy a --yyy d
+  ["--yyy", "XYZ"]
+  ["--yyy", "FOO"]
+
 === Argument Values
 
 Permissible argument values may be restricted
@@ -380,7 +403,7 @@ Executions:
       -xXXX                            Values for required argument
       -y [YYY]                         Values for optional argument
   $ ruby explicit_array_values.rb -x
-  explicit_array_values.rb:9:in `<main>': missing argument: -x (OptionParser::MissingArgument)
+  explicit_array_values.rb:9:in '<main>': missing argument: -x (OptionParser::MissingArgument)
   $ ruby explicit_array_values.rb -x foo
   ["-x", "foo"]
   $ ruby explicit_array_values.rb -x f
@@ -388,9 +411,9 @@ Executions:
   $ ruby explicit_array_values.rb -x bar
   ["-x", "bar"]
   $ ruby explicit_array_values.rb -y ba
-  explicit_array_values.rb:9:in `<main>': ambiguous argument: -y ba (OptionParser::AmbiguousArgument)
+  explicit_array_values.rb:9:in '<main>': ambiguous argument: -y ba (OptionParser::AmbiguousArgument)
   $ ruby explicit_array_values.rb -x baz
-  explicit_array_values.rb:9:in `<main>': invalid argument: -x baz (OptionParser::InvalidArgument)
+  explicit_array_values.rb:9:in '<main>': invalid argument: -x baz (OptionParser::InvalidArgument)
 
 
 ===== Explicit Values in Hash
@@ -410,7 +433,7 @@ Executions:
       -xXXX                            Values for required argument
       -y [YYY]                         Values for optional argument
   $ ruby explicit_hash_values.rb -x
-  explicit_hash_values.rb:9:in `<main>': missing argument: -x (OptionParser::MissingArgument)
+  explicit_hash_values.rb:9:in '<main>': missing argument: -x (OptionParser::MissingArgument)
   $ ruby explicit_hash_values.rb -x foo
   ["-x", 0]
   $ ruby explicit_hash_values.rb -x f
@@ -418,7 +441,7 @@ Executions:
   $ ruby explicit_hash_values.rb -x bar
   ["-x", 1]
   $ ruby explicit_hash_values.rb -x baz
-  explicit_hash_values.rb:9:in `<main>': invalid argument: -x baz (OptionParser::InvalidArgument)
+  explicit_hash_values.rb:9:in '<main>': invalid argument: -x baz (OptionParser::InvalidArgument)
   $ ruby explicit_hash_values.rb -y
   ["-y", nil]
   $ ruby explicit_hash_values.rb -y baz
@@ -426,7 +449,7 @@ Executions:
   $ ruby explicit_hash_values.rb -y bat
   ["-y", 3]
   $ ruby explicit_hash_values.rb -y ba
-  explicit_hash_values.rb:9:in `<main>': ambiguous argument: -y ba (OptionParser::AmbiguousArgument)
+  explicit_hash_values.rb:9:in '<main>': ambiguous argument: -y ba (OptionParser::AmbiguousArgument)
   $ ruby explicit_hash_values.rb -y bam
   ["-y", nil]
 
@@ -449,7 +472,7 @@ Executions:
   $ ruby matched_values.rb --xxx FOO
   ["--xxx", "FOO"]
   $ ruby matched_values.rb --xxx bar
-  matched_values.rb:6:in `<main>': invalid argument: --xxx bar (OptionParser::InvalidArgument)
+  matched_values.rb:6:in '<main>': invalid argument: --xxx bar (OptionParser::InvalidArgument)
 
 === Keyword Argument +into+
 
@@ -501,7 +524,7 @@ Executions:
       -y, --yyyYYY                     Short and long, required argument
       -z, --zzz [ZZZ]                  Short and long, optional argument
   $ ruby missing_options.rb --yyy FOO
-  missing_options.rb:11:in `<main>': Missing required options: [:xxx, :zzz] (RuntimeError)
+  missing_options.rb:11:in '<main>': Missing required options: [:xxx, :zzz] (RuntimeError)
 
 ==== Default Values for Options
 
diff --git a/lib/optparse.rb b/lib/optparse.rb
index 832b928..e1069b3 100644
--- a/lib/optparse.rb
+++ b/lib/optparse.rb
@@ -8,7 +8,6 @@
 # See OptionParser for documentation.
 #
 
-
 #--
 # == Developer Documentation (not for RDoc output)
 #
@@ -143,7 +142,7 @@
 # Used:
 #
 #   $ ruby optparse-test.rb -r
-#   optparse-test.rb:9:in `<main>': missing argument: -r (OptionParser::MissingArgument)
+#   optparse-test.rb:9:in '<main>': missing argument: -r (OptionParser::MissingArgument)
 #   $ ruby optparse-test.rb -r my-library
 #   You required my-library!
 #
@@ -236,7 +235,7 @@
 #   $ ruby optparse-test.rb --user 2
 #   #<struct User id=2, name="Gandalf">
 #   $ ruby optparse-test.rb --user 3
-#   optparse-test.rb:15:in `block in find_user': No User Found for id 3 (RuntimeError)
+#   optparse-test.rb:15:in 'block in find_user': No User Found for id 3 (RuntimeError)
 #
 # === Store options to a Hash
 #
@@ -425,7 +424,8 @@
 # If you have any questions, file a ticket at http://bugs.ruby-lang.org.
 #
 class OptionParser
-  OptionParser::Version = "0.4.0"
+  # The version string
+  OptionParser::Version = "0.7.0.dev.2"
 
   # :stopdoc:
   NoArgument = [NO_ARGUMENT = :NONE, nil].freeze
@@ -438,6 +438,8 @@ class OptionParser
   # and resolved against a list of acceptable values.
   #
   module Completion
+    # :nodoc:
+
     def self.regexp(key, icase)
       Regexp.new('\A' + Regexp.quote(key).gsub(/\w+\b/, '\&\w*'), icase)
     end
@@ -459,7 +461,11 @@ def self.candidate(key, icase = false, pat = nil, &block)
       candidates
     end
 
-    def candidate(key, icase = false, pat = nil)
+    def self.completable?(key)
+      String.try_convert(key) or defined?(key.id2name)
+    end
+
+    def candidate(key, icase = false, pat = nil, &_)
       Completion.candidate(key, icase, pat, &method(:each))
     end
 
@@ -494,7 +500,6 @@ def convert(opt = nil, val = nil, *)
     end
   end
 
-
   #
   # Map from option/keyword string to object with completion.
   #
@@ -502,7 +507,6 @@ class OptionMap < Hash
     include Completion
   end
 
-
   #
   # Individual switch class.  Not important to the user.
   #
@@ -510,6 +514,8 @@ class OptionMap < Hash
   # RequiredArgument, etc.
   #
   class Switch
+    # :nodoc:
+
     attr_reader :pattern, :conv, :short, :long, :arg, :desc, :block
 
     #
@@ -542,11 +548,11 @@ def self.pattern
 
     def initialize(pattern = nil, conv = nil,
                    short = nil, long = nil, arg = nil,
-                   desc = ([] if short or long), block = nil, &_block)
+                   desc = ([] if short or long), block = nil, values = nil, &_block)
       raise if Array === pattern
       block ||= _block
-      @pattern, @conv, @short, @long, @arg, @desc, @block =
-        pattern, conv, short, long, arg, desc, block
+      @pattern, @conv, @short, @long, @arg, @desc, @block, @values =
+        pattern, conv, short, long, arg, desc, block, values
     end
 
     #
@@ -579,11 +585,15 @@ def parse_arg(arg) # :nodoc:
     # exception.
     #
     def conv_arg(arg, val = []) # :nodoc:
+      v, = *val
       if conv
         val = conv.call(*val)
       else
         val = proc {|v| v}.call(*val)
       end
+      if @values
+        @values.include?(val) or raise InvalidArgument, v
+      end
       return arg, block, val
     end
     private :conv_arg
@@ -664,7 +674,7 @@ def compsys(sdone, ldone)   # :nodoc:
 
       (sopts+lopts).each do |opt|
         # "(-x -c -r)-l[left justify]"
-        if /^--\[no-\](.+)$/ =~ opt
+        if /\A--\[no-\](.+)$/ =~ opt
           o = $1
           yield("--#{o}", desc.join(""))
           yield("--no-#{o}", desc.join(""))
@@ -697,6 +707,11 @@ def pretty_print(q)         # :nodoc:
       q.object_group(self) {pretty_print_contents(q)}
     end
 
+    def omitted_argument(val)   # :nodoc:
+      val.pop if val.size == 3 and val.last.nil?
+      val
+    end
+
     #
     # Switch that takes no arguments.
     #
@@ -710,10 +725,10 @@ def parse(arg, argv)
         conv_arg(arg)
       end
 
-      def self.incompatible_argument_styles(*)
+      def self.incompatible_argument_styles(*) # :nodoc:
       end
 
-      def self.pattern
+      def self.pattern          # :nodoc:
         Object
       end
 
@@ -730,7 +745,7 @@ class RequiredArgument < self
       #
       # Raises an exception if argument is not present.
       #
-      def parse(arg, argv)
+      def parse(arg, argv, &_)
         unless arg
           raise MissingArgument if argv.empty?
           arg = argv.shift
@@ -755,7 +770,7 @@ def parse(arg, argv, &error)
         if arg
           conv_arg(*parse_arg(arg, &error))
         else
-          conv_arg(arg)
+          omitted_argument conv_arg(arg)
         end
       end
 
@@ -774,13 +789,14 @@ class PlacedArgument < self
       #
       def parse(arg, argv, &error)
         if !(val = arg) and (argv.empty? or /\A-./ =~ (val = argv[0]))
-          return nil, block, nil
+          return nil, block
         end
         opt = (val = parse_arg(val, &error))[1]
         val = conv_arg(*val)
         if opt and !arg
           argv.shift
         else
+          omitted_argument val
           val[0] = nil
         end
         val
@@ -798,6 +814,8 @@ def pretty_head           # :nodoc:
   # matching pattern and converter pair. Also provides summary feature.
   #
   class List
+    # :nodoc:
+
     # Map from acceptable argument types to pattern and converter pairs.
     attr_reader :atype
 
@@ -837,7 +855,7 @@ def pretty_print(q)         # :nodoc:
     def accept(t, pat = /.*/m, &block)
       if pat
         pat.respond_to?(:match) or
-          raise TypeError, "has no `match'", ParseError.filter_backtrace(caller(2))
+          raise TypeError, "has no 'match'", ParseError.filter_backtrace(caller(2))
       else
         pat = t if t.respond_to?(:match)
       end
@@ -1020,7 +1038,6 @@ def match(key)
   DefaultList.short['-'] = Switch::NoArgument.new {}
   DefaultList.long[''] = Switch::NoArgument.new {throw :terminate}
 
-
   COMPSYS_HEADER = <<'XXX'      # :nodoc:
 
 typeset -A opt_args
@@ -1033,11 +1050,31 @@ def compsys(to, name = File.basename($0)) # :nodoc:
     to << "#compdef #{name}\n"
     to << COMPSYS_HEADER
     visit(:compsys, {}, {}) {|o, d|
-      to << %Q[  "#{o}[#{d.gsub(/[\"\[\]]/, '\\\\\&')}]" \\\n]
+      to << %Q[  "#{o}[#{d.gsub(/[\\\"\[\]]/, '\\\\\&')}]" \\\n]
     }
     to << "  '*:file:_files' && return 0\n"
   end
 
+  def help_exit
+    if $stdout.tty? && (pager = ENV.values_at(*%w[RUBY_PAGER PAGER]).find {|e| e && !e.empty?})
+      less = ENV["LESS"]
+      args = [{"LESS" => "#{less} -Fe"}, pager, "w"]
+      print = proc do |f|
+        f.puts help
+      rescue Errno::EPIPE
+        # pager terminated
+      end
+      if Process.respond_to?(:fork) and false
+        IO.popen("-") {|f| f ? Process.exec(*args, in: f) : print.call($stdout)}
+        # unreachable
+      end
+      IO.popen(*args, &print)
+    else
+      puts help
+    end
+    exit
+  end
+
   #
   # Default options for ARGV, which never appear in option summary.
   #
@@ -1049,8 +1086,7 @@ def compsys(to, name = File.basename($0)) # :nodoc:
   #
   Officious['help'] = proc do |parser|
     Switch::NoArgument.new do |arg|
-      puts parser.help
-      exit
+      parser.help_exit
     end
   end
 
@@ -1071,7 +1107,7 @@ def compsys(to, name = File.basename($0)) # :nodoc:
   #
   Officious['*-completion-zsh'] = proc do |parser|
     Switch::OptionalArgument.new do |arg|
-      parser.compsys(STDOUT, arg)
+      parser.compsys($stdout, arg)
       exit
     end
   end
@@ -1084,7 +1120,7 @@ def compsys(to, name = File.basename($0)) # :nodoc:
     Switch::OptionalArgument.new do |pkg|
       if pkg
         begin
-          require 'optparse/version'
+          require_relative 'optparse/version'
         rescue LoadError
         else
           show_version(*pkg.split(/,/)) or
@@ -1129,6 +1165,10 @@ def self.inc(arg, default = nil)
       default.to_i + 1
     end
   end
+
+  #
+  # See self.inc
+  #
   def inc(*args)
     self.class.inc(*args)
   end
@@ -1167,11 +1207,19 @@ def add_officious  # :nodoc:
   def terminate(arg = nil)
     self.class.terminate(arg)
   end
+  #
+  # See #terminate.
+  #
   def self.terminate(arg = nil)
     throw :terminate, arg
   end
 
   @stack = [DefaultList]
+  #
+  # Returns the global top option list.
+  #
+  # Do not use directly.
+  #
   def self.top() DefaultList end
 
   #
@@ -1192,9 +1240,9 @@ def self.accept(*args, &blk) top.accept(*args, &blk) end
   #
   # Directs to reject specified class argument.
   #
-  # +t+:: Argument class specifier, any object including Class.
+  # +type+:: Argument class specifier, any object including Class.
   #
-  #   reject(t)
+  #   reject(type)
   #
   def reject(*args, &blk) top.reject(*args, &blk) end
   #
@@ -1284,10 +1332,24 @@ def ver
     end
   end
 
+  #
+  # Shows warning message with the program name
+  #
+  # +mesg+:: Message, defaulted to +$!+.
+  #
+  # See Kernel#warn.
+  #
   def warn(mesg = $!)
     super("#{program_name}: #{mesg}")
   end
 
+  #
+  # Shows message with the program name then aborts.
+  #
+  # +mesg+:: Message, defaulted to +$!+.
+  #
+  # See Kernel#abort.
+  #
   def abort(mesg = $!)
     super("#{program_name}: #{mesg}")
   end
@@ -1309,6 +1371,9 @@ def base
   #
   # Pushes a new List.
   #
+  # If a block is given, yields +self+ and returns the result of the
+  # block, otherwise returns +self+.
+  #
   def new
     @stack.push(List.new)
     if block_given?
@@ -1407,6 +1472,7 @@ def make_switch(opts, block = nil)
     klass = nil
     q, a = nil
     has_arg = false
+    values = nil
 
     opts.each do |o|
       # argument class
@@ -1420,7 +1486,7 @@ def make_switch(opts, block = nil)
       end
 
       # directly specified pattern(any object possible to match)
-      if (!(String === o || Symbol === o)) and o.respond_to?(:match)
+      if !Completion.completable?(o) and o.respond_to?(:match)
         pattern = notwice(o, pattern, 'pattern')
         if pattern.respond_to?(:convert)
           conv = pattern.method(:convert).to_proc
@@ -1435,6 +1501,11 @@ def make_switch(opts, block = nil)
       when Proc, Method
         block = notwice(o, block, 'block')
       when Array, Hash
+        if Array === o
+          o, v = o.partition {|v,| Completion.completable?(v)}
+          values = notwice(v, values, 'values') unless v.empty?
+          next if o.empty?
+        end
         case pattern
         when CompletingHash
         when nil
@@ -1444,11 +1515,13 @@ def make_switch(opts, block = nil)
           raise ArgumentError, "argument pattern given twice"
         end
         o.each {|pat, *v| pattern[pat] = v.fetch(0) {pat}}
+      when Range
+        values = notwice(o, values, 'values')
       when Module
         raise ArgumentError, "unsupported argument type: #{o}", ParseError.filter_backtrace(caller(4))
       when *ArgumentStyle.keys
         style = notwice(ArgumentStyle[o], style, 'style')
-      when /^--no-([^\[\]=\s]*)(.+)?/
+      when /\A--no-([^\[\]=\s]*)(.+)?/
         q, a = $1, $2
         o = notwice(a ? Object : TrueClass, klass, 'type')
         not_pattern, not_conv = search(:atype, o) unless not_style
@@ -1459,7 +1532,7 @@ def make_switch(opts, block = nil)
         (q = q.downcase).tr!('_', '-')
         long << "no-#{q}"
         nolong << q
-      when /^--\[no-\]([^\[\]=\s]*)(.+)?/
+      when /\A--\[no-\]([^\[\]=\s]*)(.+)?/
         q, a = $1, $2
         o = notwice(a ? Object : TrueClass, klass, 'type')
         if a
@@ -1472,7 +1545,7 @@ def make_switch(opts, block = nil)
         not_pattern, not_conv = search(:atype, FalseClass) unless not_style
         not_style = Switch::NoArgument
         nolong << "no-#{o}"
-      when /^--([^\[\]=\s]*)(.+)?/
+      when /\A--([^\[\]=\s]*)(.+)?/
         q, a = $1, $2
         if a
           o = notwice(NilClass, klass, 'type')
@@ -1482,7 +1555,7 @@ def make_switch(opts, block = nil)
         ldesc << "--#{q}"
         (o = q.downcase).tr!('_', '-')
         long << o
-      when /^-(\[\^?\]?(?:[^\\\]]|\\.)*\])(.+)?/
+      when /\A-(\[\^?\]?(?:[^\\\]]|\\.)*\])(.+)?/
         q, a = $1, $2
         o = notwice(Object, klass, 'type')
         if a
@@ -1493,7 +1566,7 @@ def make_switch(opts, block = nil)
         end
         sdesc << "-#{q}"
         short << Regexp.new(q)
-      when /^-(.)(.+)?/
+      when /\A-(.)(.+)?/
         q, a = $1, $2
         if a
           o = notwice(NilClass, klass, 'type')
@@ -1502,7 +1575,7 @@ def make_switch(opts, block = nil)
         end
         sdesc << "-#{q}"
         short << q
-      when /^=/
+      when /\A=/
         style = notwice(default_style.guess(arg = o), style, 'style')
         default_pattern, conv = search(:atype, Object) unless default_pattern
       else
@@ -1511,12 +1584,18 @@ def make_switch(opts, block = nil)
     end
 
     default_pattern, conv = search(:atype, default_style.pattern) unless default_pattern
+    if Range === values and klass
+      unless (!values.begin or klass === values.begin) and
+            (!values.end or klass === values.end)
+        raise ArgumentError, "range does not match class"
+      end
+    end
     if !(short.empty? and long.empty?)
       if has_arg and default_style == Switch::NoArgument
         default_style = Switch::RequiredArgument
       end
       s = (style || default_style).new(pattern || default_pattern,
-                                       conv, sdesc, ldesc, arg, desc, block)
+                                       conv, sdesc, ldesc, arg, desc, block, values)
     elsif !block
       if style or pattern
         raise ArgumentError, "no switch given", ParseError.filter_backtrace(caller)
@@ -1525,13 +1604,19 @@ def make_switch(opts, block = nil)
     else
       short << pattern
       s = (style || default_style).new(pattern,
-                                       conv, nil, nil, arg, desc, block)
+                                       conv, nil, nil, arg, desc, block, values)
     end
     return s, short, long,
       (not_style.new(not_pattern, not_conv, sdesc, ldesc, nil, desc, block) if not_style),
       nolong
   end
 
+  # ----
+  # Option definition phase methods
+  #
+  # These methods are used to define options, or to construct an
+  # OptionParser instance in other words.
+
   # :call-seq:
   #   define(*params, &block)
   #
@@ -1607,6 +1692,13 @@ def separator(string)
     top.append(string, nil, nil)
   end
 
+  # ----
+  # Arguments parse phase methods
+  #
+  # These methods parse +argv+, convert, and store the results by
+  # calling handlers.  As these methods do not modify +self+, +self+
+  # can be frozen.
+
   #
   # Parses command line arguments +argv+ in order. When a block is given,
   # each non-option argument is yielded. When optional +into+ keyword
@@ -1616,21 +1708,21 @@ def separator(string)
   #
   # Returns the rest of +argv+ left unparsed.
   #
-  def order(*argv, into: nil, &nonopt)
+  def order(*argv, **keywords, &nonopt)
     argv = argv[0].dup if argv.size == 1 and Array === argv[0]
-    order!(argv, into: into, &nonopt)
+    order!(argv, **keywords, &nonopt)
   end
 
   #
   # Same as #order, but removes switches destructively.
   # Non-option arguments remain in +argv+.
   #
-  def order!(argv = default_argv, into: nil, &nonopt)
+  def order!(argv = default_argv, into: nil, **keywords, &nonopt)
     setter = ->(name, val) {into[name.to_sym] = val} if into
-    parse_in_order(argv, setter, &nonopt)
+    parse_in_order(argv, setter, **keywords, &nonopt)
   end
 
-  def parse_in_order(argv = default_argv, setter = nil, &nonopt)  # :nodoc:
+  def parse_in_order(argv = default_argv, setter = nil, exact: require_exact, **, &nonopt)  # :nodoc:
     opt, arg, val, rest = nil
     nonopt ||= proc {|a| throw :terminate, a}
     argv.unshift(arg) if arg = catch(:terminate) {
@@ -1641,19 +1733,24 @@ def parse_in_order(argv = default_argv, setter = nil, &nonopt)  # :nodoc:
           opt, rest = $1, $2
           opt.tr!('_', '-')
           begin
-            sw, = complete(:long, opt, true)
-            if require_exact && !sw.long.include?(arg)
-              throw :terminate, arg unless raise_unknown
-              raise InvalidOption, arg
+            if exact
+              sw, = search(:long, opt)
+            else
+              sw, = complete(:long, opt, true)
             end
           rescue ParseError
             throw :terminate, arg unless raise_unknown
             raise $!.set_option(arg, true)
+          else
+            unless sw
+              throw :terminate, arg unless raise_unknown
+              raise InvalidOption, arg
+            end
           end
           begin
             opt, cb, val = sw.parse(rest, argv) {|*exc| raise(*exc)}
-            val = cb.call(val) if cb
-            setter.call(sw.switch_name, val) if setter
+            val = callback!(cb, 1, val) if cb
+            callback!(setter, 2, sw.switch_name, val) if setter
           rescue ParseError
             raise $!.set_option(arg, rest)
           end
@@ -1671,7 +1768,7 @@ def parse_in_order(argv = default_argv, setter = nil, &nonopt)  # :nodoc:
                 val = arg.delete_prefix('-')
                 has_arg = true
               rescue InvalidOption
-                raise if require_exact
+                raise if exact
                 # if no short options match, try completion with long
                 # options.
                 sw, = complete(:long, opt)
@@ -1691,8 +1788,8 @@ def parse_in_order(argv = default_argv, setter = nil, &nonopt)  # :nodoc:
           end
           begin
             argv.unshift(opt) if opt and (!rest or (opt = opt.sub(/\A-*/, '-')) != '-')
-            val = cb.call(val) if cb
-            setter.call(sw.switch_name, val) if setter
+            val = callback!(cb, 1, val) if cb
+            callback!(setter, 2, sw.switch_name, val) if setter
           rescue ParseError
             raise $!.set_option(arg, arg.length > 2)
           end
@@ -1718,6 +1815,19 @@ def parse_in_order(argv = default_argv, setter = nil, &nonopt)  # :nodoc:
   end
   private :parse_in_order
 
+  # Calls callback with _val_.
+  def callback!(cb, max_arity, *args) # :nodoc:
+    args.compact!
+
+    if (size = args.size) < max_arity and cb.to_proc.lambda?
+      (arity = cb.arity) < 0 and arity = (1-arity)
+      arity = max_arity if arity > max_arity
+      args[arity - 1] = nil if arity > size
+    end
+    cb.call(*args)
+  end
+  private :callback!
+
   #
   # Parses command line arguments +argv+ in permutation mode and returns
   # list of non-option arguments. When optional +into+ keyword
@@ -1725,18 +1835,18 @@ def parse_in_order(argv = default_argv, setter = nil, &nonopt)  # :nodoc:
   # <code>[]=</code> method (so it can be Hash, or OpenStruct, or other
   # similar object).
   #
-  def permute(*argv, into: nil)
+  def permute(*argv, **keywords)
     argv = argv[0].dup if argv.size == 1 and Array === argv[0]
-    permute!(argv, into: into)
+    permute!(argv, **keywords)
   end
 
   #
   # Same as #permute, but removes switches destructively.
   # Non-option arguments remain in +argv+.
   #
-  def permute!(argv = default_argv, into: nil)
+  def permute!(argv = default_argv, **keywords)
     nonopts = []
-    order!(argv, into: into, &nonopts.method(:<<))
+    order!(argv, **keywords, &nonopts.method(:<<))
     argv[0, 0] = nonopts
     argv
   end
@@ -1748,20 +1858,20 @@ def permute!(argv = default_argv, into: nil)
   # values are stored there via <code>[]=</code> method (so it can be Hash,
   # or OpenStruct, or other similar object).
   #
-  def parse(*argv, into: nil)
+  def parse(*argv, **keywords)
     argv = argv[0].dup if argv.size == 1 and Array === argv[0]
-    parse!(argv, into: into)
+    parse!(argv, **keywords)
   end
 
   #
   # Same as #parse, but removes switches destructively.
   # Non-option arguments remain in +argv+.
   #
-  def parse!(argv = default_argv, into: nil)
+  def parse!(argv = default_argv, **keywords)
     if ENV.include?('POSIXLY_CORRECT')
-      order!(argv, into: into)
+      order!(argv, **keywords)
     else
-      permute!(argv, into: into)
+      permute!(argv, **keywords)
     end
   end
 
@@ -1784,7 +1894,7 @@ def parse!(argv = default_argv, into: nil)
   #   # params[:bar] = "x"  # --bar x
   #   # params[:zot] = "z"  # --zot Z
   #
-  def getopts(*args, symbolize_names: false)
+  def getopts(*args, symbolize_names: false, **keywords)
     argv = Array === args.first ? args.shift : default_argv
     single_options, *long_options = *args
 
@@ -1812,7 +1922,7 @@ def getopts(*args, symbolize_names: false)
       end
     end
 
-    parse_in_order(argv, result.method(:[]=))
+    parse_in_order(argv, result.method(:[]=), **keywords)
     symbolize_names ? result.transform_keys(&:to_sym) : result
   end
 
@@ -1881,6 +1991,9 @@ def additional_message(typ, opt)
     DidYouMean.formatter.message_for(all_candidates & checker.correct(opt))
   end
 
+  #
+  # Return candidates for +word+.
+  #
   def candidate(word)
     list = []
     case word
@@ -1922,10 +2035,10 @@ def candidate(word)
   # The optional +into+ keyword argument works exactly like that accepted in
   # method #parse.
   #
-  def load(filename = nil, into: nil)
+  def load(filename = nil, **keywords)
     unless filename
       basename = File.basename($0, '.*')
-      return true if load(File.expand_path(basename, '~/.options'), into: into) rescue nil
+      return true if load(File.expand_path(basename, '~/.options'), **keywords) rescue nil
       basename << ".options"
       return [
         # XDG
@@ -1937,11 +2050,11 @@ def load(filename = nil, into: nil)
         '~/config/settings',
       ].any? {|dir|
         next if !dir or dir.empty?
-        load(File.expand_path(basename, dir), into: into) rescue nil
+        load(File.expand_path(basename, dir), **keywords) rescue nil
       }
     end
     begin
-      parse(*File.readlines(filename, chomp: true), into: into)
+      parse(*File.readlines(filename, chomp: true), **keywords)
       true
     rescue Errno::ENOENT, Errno::ENOTDIR
       false
@@ -1954,10 +2067,10 @@ def load(filename = nil, into: nil)
   #
   # +env+ defaults to the basename of the program.
   #
-  def environment(env = File.basename($0, '.*'))
+  def environment(env = File.basename($0, '.*'), **keywords)
     env = ENV[env] || ENV[env.upcase] or return
     require 'shellwords'
-    parse(*Shellwords.shellwords(env))
+    parse(*Shellwords.shellwords(env), **keywords)
   end
 
   #
@@ -2123,6 +2236,7 @@ class ParseError < RuntimeError
     # Reason which caused the error.
     Reason = 'parse error'
 
+    # :nodoc:
     def initialize(*args, additional: nil)
       @additional = additional
       @arg0, = args
@@ -2273,19 +2387,19 @@ def options
     # Parses +self+ destructively in order and returns +self+ containing the
     # rest arguments left unparsed.
     #
-    def order!(&blk) options.order!(self, &blk) end
+    def order!(**keywords, &blk) options.order!(self, **keywords, &blk) end
 
     #
     # Parses +self+ destructively in permutation mode and returns +self+
     # containing the rest arguments left unparsed.
     #
-    def permute!() options.permute!(self) end
+    def permute!(**keywords) options.permute!(self, **keywords) end
 
     #
     # Parses +self+ destructively and returns +self+ containing the
     # rest arguments left unparsed.
     #
-    def parse!() options.parse!(self) end
+    def parse!(**keywords) options.parse!(self, **keywords) end
 
     #
     # Substitution of getopts is possible as follows. Also see
@@ -2298,8 +2412,8 @@ def parse!() options.parse!(self) end
     #   rescue OptionParser::ParseError
     #   end
     #
-    def getopts(*args, symbolize_names: false)
-      options.getopts(self, *args, symbolize_names: symbolize_names)
+    def getopts(*args, symbolize_names: false, **keywords)
+      options.getopts(self, *args, symbolize_names: symbolize_names, **keywords)
     end
 
     #
@@ -2309,7 +2423,8 @@ def self.extend_object(obj)
       super
       obj.instance_eval {@optparse = nil}
     end
-    def initialize(*args)
+
+    def initialize(*args)       # :nodoc:
       super
       @optparse = nil
     end
diff --git a/lib/optparse/ac.rb b/lib/optparse/ac.rb
index 0953725..23fc740 100644
--- a/lib/optparse/ac.rb
+++ b/lib/optparse/ac.rb
@@ -1,7 +1,11 @@
 # frozen_string_literal: false
 require_relative '../optparse'
 
+#
+# autoconf-like options.
+#
 class OptionParser::AC < OptionParser
+  # :stopdoc:
   private
 
   def _check_ac_args(name, block)
@@ -14,6 +18,7 @@ def _check_ac_args(name, block)
   end
 
   ARG_CONV = proc {|val| val.nil? ? true : val}
+  private_constant :ARG_CONV
 
   def _ac_arg_enable(prefix, name, help_string, block)
     _check_ac_args(name, block)
@@ -29,16 +34,27 @@ def _ac_arg_enable(prefix, name, help_string, block)
     enable
   end
 
+  # :startdoc:
+
   public
 
+  # Define <tt>--enable</tt> / <tt>--disable</tt> style option
+  #
+  # Appears as <tt>--enable-<i>name</i></tt> in help message.
   def ac_arg_enable(name, help_string, &block)
     _ac_arg_enable("enable", name, help_string, block)
   end
 
+  # Define <tt>--enable</tt> / <tt>--disable</tt> style option
+  #
+  # Appears as <tt>--disable-<i>name</i></tt> in help message.
   def ac_arg_disable(name, help_string, &block)
     _ac_arg_enable("disable", name, help_string, block)
   end
 
+  # Define <tt>--with</tt> / <tt>--without</tt> style option
+  #
+  # Appears as <tt>--with-<i>name</i></tt> in help message.
   def ac_arg_with(name, help_string, &block)
     _check_ac_args(name, block)
 
diff --git a/lib/optparse/kwargs.rb b/lib/optparse/kwargs.rb
index 992aca4..59a2f61 100644
--- a/lib/optparse/kwargs.rb
+++ b/lib/optparse/kwargs.rb
@@ -7,12 +7,17 @@ class OptionParser
   #
   # :include: ../../doc/optparse/creates_option.rdoc
   #
-  def define_by_keywords(options, meth, **opts)
-    meth.parameters.each do |type, name|
+  # Defines options which set in to _options_ for keyword parameters
+  # of _method_.
+  #
+  # Parameters for each keywords are given as elements of _params_.
+  #
+  def define_by_keywords(options, method, **params)
+    method.parameters.each do |type, name|
       case type
       when :key, :keyreq
         op, cl = *(type == :key ? %w"[ ]" : ["", ""])
-        define("--#{name}=#{op}#{name.upcase}#{cl}", *opts[name]) do |o|
+        define("--#{name}=#{op}#{name.upcase}#{cl}", *params[name]) do |o|
           options[name] = o
         end
       end
diff --git a/lib/optparse/version.rb b/lib/optparse/version.rb
index b869d8f..b5ed695 100644
--- a/lib/optparse/version.rb
+++ b/lib/optparse/version.rb
@@ -2,6 +2,11 @@
 # OptionParser internal utility
 
 class << OptionParser
+  #
+  # Shows version string in packages if Version is defined.
+  #
+  # +pkgs+:: package list
+  #
   def show_version(*pkgs)
     progname = ARGV.options.program_name
     result = false
@@ -47,6 +52,8 @@ def show_version(*pkgs)
     result
   end
 
+  # :stopdoc:
+
   def each_const(path, base = ::Object)
     path.split(/::|\//).inject(base) do |klass, name|
       raise NameError, path unless Module === klass
@@ -68,4 +75,6 @@ def search_const(klass, name)
       end
     end
   end
+
+  # :startdoc:
 end
diff --git a/optparse.gemspec b/optparse.gemspec
index a4287dd..8589f18 100644
--- a/optparse.gemspec
+++ b/optparse.gemspec
@@ -14,7 +14,10 @@ Gem::Specification.new do |spec|
   spec.email         = ["nobu@ruby-lang.org"]
 
   spec.summary       = %q{OptionParser is a class for command-line option analysis.}
-  spec.description   = %q{OptionParser is a class for command-line option analysis.}
+  spec.description   = File.open(File.join(__dir__, "README.md")) do |readme|
+    readme.gets("") # heading
+    readme.gets("").chomp
+  end rescue spec.summary
   spec.homepage      = "https://github.com/ruby/optparse"
   spec.required_ruby_version = Gem::Requirement.new(">= 2.5.0")
   spec.licenses      = ["Ruby", "BSD-2-Clause"]
@@ -22,8 +25,8 @@ Gem::Specification.new do |spec|
   spec.metadata["homepage_uri"] = spec.homepage
   spec.metadata["source_code_uri"] = spec.homepage
 
-  spec.files         = Dir["{doc,lib,misc}/**/*"] + %w[README.md ChangeLog COPYING]
-  spec.rdoc_options  = ["--main=README.md", "--op=rdoc", "--page-dir=doc"]
+  spec.files         = Dir["{doc,lib,misc}/**/{*,.document}"] +
+                       %w[README.md ChangeLog COPYING .document .rdoc_options]
   spec.bindir        = "exe"
   spec.executables   = []
   spec.require_paths = ["lib"]
diff --git a/rakelib/changelogs.rake b/rakelib/changelogs.rake
index df72f9d..9be2e8a 100644
--- a/rakelib/changelogs.rake
+++ b/rakelib/changelogs.rake
@@ -3,7 +3,10 @@ task "build" => "changelogs"
 changelog = proc do |output, ver = nil, prev = nil|
   ver &&= Gem::Version.new(ver)
   range = [[prev], [ver, "HEAD"]].map {|ver, branch| ver ? "v#{ver.to_s}" : branch}.compact.join("..")
-  IO.popen(%W[git log --format=fuller --topo-order --no-merges #{range}]) do |log|
+  cmd = %W[git log --date=iso --format=fuller --topo-order --no-merges
+               --invert-grep --fixed-strings --grep=#{'[ci skip]'}
+               #{range} --]
+  IO.popen(cmd) do |log|
     line = log.gets
     FileUtils.mkpath(File.dirname(output))
     File.open(output, "wb") do |f|
@@ -18,10 +21,13 @@ changelog = proc do |output, ver = nil, prev = nil|
 end
 
 tags = IO.popen(%w[git tag -l v[0-9]*]).grep(/v(.*)/) {$1}
-tags.sort_by! {|tag| tag.scan(/\d+/).map(&:to_i)}
-tags.inject(nil) do |prev, tag|
-  task("logs/ChangeLog-#{tag}") {|t| changelog[t.name, tag, prev]}
-  tag
+unless tags.empty?
+  tags.sort_by! {|tag| tag.scan(/\d+/).map(&:to_i)}
+  tags.pop if IO.popen(%W[git rev-list --right-only --count v#{tags.last}..HEAD --], &:read).to_i == 0
+  tags.inject(nil) do |prev, tag|
+    task("logs/ChangeLog-#{tag}") {|t| changelog[t.name, tag, prev]}
+    tag
+  end
 end
 
 desc "Make ChangeLog"
diff --git a/rakelib/version.rake b/rakelib/version.rake
index eb430b0..583530d 100644
--- a/rakelib/version.rake
+++ b/rakelib/version.rake
@@ -28,9 +28,21 @@ class << (helper = Bundler::GemHelper.instance)
   def bump(major, minor = 0, teeny = 0, pre: nil)
     self.version = [major, minor, teeny, pre].compact.join(".")
   end
+
+  def next_prerelease(*prefix, num)
+    if num
+      [*prefix, num.succ]
+    else
+      "dev.1"
+    end
+  end
 end
 
-major, minor, teeny = helper.gemspec.version.segments
+major, minor, teeny, *prerelease = helper.gemspec.version.segments
+
+task "bump:dev", [:pre] do |t, pre: helper.next_prerelease(*prerelease)|
+  helper.bump(major, minor, teeny, pre: pre)
+end
 
 task "bump:teeny", [:pre] do |t, pre: nil|
   helper.bump(major, minor, teeny+1, pre: pre)
diff --git a/test/optparse/test_acceptable.rb b/test/optparse/test_acceptable.rb
index 12f5322..8b578ef 100644
--- a/test/optparse/test_acceptable.rb
+++ b/test/optparse/test_acceptable.rb
@@ -8,6 +8,7 @@ def setup
     @opt.def_option("--integer VAL", Integer) { |v| @integer = v }
     @opt.def_option("--float VAL",   Float)   { |v| @float   = v }
     @opt.def_option("--numeric VAL", Numeric) { |v| @numeric = v }
+    @opt.def_option("--array VAL", Array) { |v| @array = v }
 
     @opt.def_option("--decimal-integer VAL",
                     OptionParser::DecimalInteger) { |i| @decimal_integer = i }
@@ -195,4 +196,10 @@ def test_decimal_numeric
     end
   end
 
+  def test_array
+    assert_equal(%w"", no_error {@opt.parse!(%w"--array a,b,c")})
+    assert_equal(%w"a b c", @array)
+    assert_equal(%w"", no_error {@opt.parse!(%w"--array a")})
+    assert_equal(%w"a", @array)
+  end
 end
diff --git a/test/optparse/test_optarg.rb b/test/optparse/test_optarg.rb
index 81127a8..f944605 100644
--- a/test/optparse/test_optarg.rb
+++ b/test/optparse/test_optarg.rb
@@ -9,6 +9,8 @@ def setup
     @opt.def_option("--regexp[=REGEXP]", Regexp) {|x| @reopt = x}
     @opt.def_option "--with_underscore[=VAL]" do |x| @flag = x end
     @opt.def_option "--with-hyphen[=VAL]" do |x| @flag = x end
+    @opt.def_option("--fallback[=VAL]") do |x = "fallback"| @flag = x end
+    @opt.def_option("--lambda[=VAL]", &->(x) {@flag = x})
     @reopt = nil
   end
 
@@ -57,4 +59,18 @@ def test_hyphenize
     assert_equal(%w"", no_error {@opt.parse!(%w"--with_hyphen=foo4")})
     assert_equal("foo4", @flag)
   end
+
+  def test_default_argument
+    assert_equal(%w"", no_error {@opt.parse!(%w"--fallback=val1")})
+    assert_equal("val1", @flag)
+    assert_equal(%w"", no_error {@opt.parse!(%w"--fallback")})
+    assert_equal("fallback", @flag)
+  end
+
+  def test_lambda
+    assert_equal(%w"", no_error {@opt.parse!(%w"--lambda=lambda1")})
+    assert_equal("lambda1", @flag)
+    assert_equal(%w"", no_error {@opt.parse!(%w"--lambda")})
+    assert_equal(nil, @flag)
+  end
 end
diff --git a/test/optparse/test_optparse.rb b/test/optparse/test_optparse.rb
index bfa705a..d50203b 100644
--- a/test/optparse/test_optparse.rb
+++ b/test/optparse/test_optparse.rb
@@ -73,10 +73,30 @@ def test_into
     @opt.def_option "-p", "--port=PORT", "port", Integer
     @opt.def_option "-v", "--verbose" do @verbose = true end
     @opt.def_option "-q", "--quiet" do @quiet = true end
+    @opt.def_option "-o", "--option [OPT]" do |opt| @option = opt end
+    @opt.def_option "-a", "--array [VAL]", Array do |val| val end
     result = {}
     @opt.parse %w(--host localhost --port 8000 -v), into: result
     assert_equal({host: "localhost", port: 8000, verbose: true}, result)
     assert_equal(true, @verbose)
+    result = {}
+    @opt.parse %w(--option -q), into: result
+    assert_equal({quiet: true, option: nil}, result)
+    result = {}
+    @opt.parse %w(--option OPTION -v), into: result
+    assert_equal({verbose: true, option: "OPTION"}, result)
+    result = {}
+    @opt.parse %w(-a b,c,d), into: result
+    assert_equal({array: %w(b c d)}, result)
+    result = {}
+    @opt.parse %w(--array b,c,d), into: result
+    assert_equal({array: %w(b c d)}, result)
+    result = {}
+    @opt.parse %w(-a b), into: result
+    assert_equal({array: %w(b)}, result)
+    result = {}
+    @opt.parse %w(--array b), into: result
+    assert_equal({array: %w(b)}, result)
   end
 
   def test_require_exact
@@ -88,9 +108,9 @@ def test_require_exact
     end
 
     @opt.require_exact = true
-    %w(--zrs -F -Ffoo).each do |arg|
+    [%w(--zrs foo), %w(--zrs=foo), %w(-F foo), %w(-Ffoo)].each do |args|
       result = {}
-      @opt.parse([arg, 'foo'], into: result)
+      @opt.parse(args, into: result)
       assert_equal({zrs: 'foo'}, result)
     end
 
@@ -99,6 +119,43 @@ def test_require_exact
     assert_raise(OptionParser::InvalidOption) {@opt.parse(%w(-zrs foo))}
     assert_raise(OptionParser::InvalidOption) {@opt.parse(%w(-zr foo))}
     assert_raise(OptionParser::InvalidOption) {@opt.parse(%w(-z foo))}
+
+    @opt.def_option('-f', '--[no-]foo', 'foo') {|arg| @foo = arg}
+    @opt.parse(%w[-f])
+    assert_equal(true, @foo)
+    @opt.parse(%w[--foo])
+    assert_equal(true, @foo)
+    @opt.parse(%w[--no-foo])
+    assert_equal(false, @foo)
+  end
+
+  def test_exact_option
+    @opt.def_option('-F', '--zrs=IRS', 'zrs')
+    %w(--zrs --zr --z -zfoo -z -F -Ffoo).each do |arg|
+      result = {}
+      @opt.parse([arg, 'foo'], into: result)
+      assert_equal({zrs: 'foo'}, result)
+    end
+
+    [%w(--zrs foo), %w(--zrs=foo), %w(-F foo), %w(-Ffoo)].each do |args|
+      result = {}
+      @opt.parse(args, into: result, exact: true)
+      assert_equal({zrs: 'foo'}, result)
+    end
+
+    assert_raise(OptionParser::InvalidOption) {@opt.parse(%w(--zr foo), exact: true)}
+    assert_raise(OptionParser::InvalidOption) {@opt.parse(%w(--z foo), exact: true)}
+    assert_raise(OptionParser::InvalidOption) {@opt.parse(%w(-zrs foo), exact: true)}
+    assert_raise(OptionParser::InvalidOption) {@opt.parse(%w(-zr foo), exact: true)}
+    assert_raise(OptionParser::InvalidOption) {@opt.parse(%w(-z foo), exact: true)}
+
+    @opt.def_option('-f', '--[no-]foo', 'foo') {|arg| @foo = arg}
+    @opt.parse(%w[-f], exact: true)
+    assert_equal(true, @foo)
+    @opt.parse(%w[--foo], exact: true)
+    assert_equal(true, @foo)
+    @opt.parse(%w[--no-foo], exact: true)
+    assert_equal(false, @foo)
   end
 
   def test_raise_unknown
@@ -120,4 +177,43 @@ def test_nonopt_pattern
     e = assert_raise(OptionParser::InvalidOption) {@opt.parse(%w(-t))}
     assert_equal(["-t"], e.args)
   end
+
+  def test_help_pager
+    require 'tmpdir'
+    Dir.mktmpdir do |dir|
+      File.open(File.join(dir, "options.rb"), "w") do |f|
+        f.puts "#{<<~"begin;"}\n#{<<~'end;'}"
+        begin;
+          stdout = $stdout.dup
+          def stdout.tty?; true; end
+          $stdout = stdout
+          ARGV.options do |opt|
+          end;
+          100.times {|i| f.puts "  opt.on('--opt-#{i}') {}"}
+          f.puts "#{<<~"begin;"}\n#{<<~'end;'}"
+          begin;
+            opt.parse!
+          end
+        end;
+      end
+
+      optparse = $".find {|path| path.end_with?("/optparse.rb")}
+      args = ["-r#{optparse}", "options.rb", "--help"]
+      cmd = File.join(dir, "pager.cmd")
+      if RbConfig::CONFIG["EXECUTABLE_EXTS"]&.include?(".cmd")
+        command = "@echo off"
+      else # if File.executable?("/bin/sh")
+        # TruffleRuby just calls `posix_spawnp` and no fallback to `/bin/sh`.
+        command = "#!/bin/sh\n"
+      end
+
+      [
+        [{"RUBY_PAGER"=>cmd, "PAGER"=>"echo ng"}, "Executing RUBY_PAGER"],
+        [{"RUBY_PAGER"=>nil, "PAGER"=>cmd}, "Executing PAGER"],
+      ].each do |env, expected|
+        File.write(cmd, "#{command}\n" "echo #{expected}\n", perm: 0o700)
+        assert_in_out_err([env, *args], "", [expected], chdir: dir)
+      end
+    end
+  end
 end
diff --git a/test/optparse/test_placearg.rb b/test/optparse/test_placearg.rb
index ed0e4d3..d5be5a6 100644
--- a/test/optparse/test_placearg.rb
+++ b/test/optparse/test_placearg.rb
@@ -7,12 +7,18 @@ def setup
     @opt.def_option("-x [VAL]") {|x| @flag = x}
     @opt.def_option("--option [VAL]") {|x| @flag = x}
     @opt.def_option("-T [level]", /^[0-4]$/, Integer) {|x| @topt = x}
+    @opt.def_option("--enum [VAL]", [:Alpha, :Bravo, :Charlie]) {|x| @enum = x}
+    @opt.def_option("--enumval [VAL]", [[:Alpha, 1], [:Bravo, 2], [:Charlie, 3]]) {|x| @enum = x}
+    @opt.def_option("--integer [VAL]", Integer, [1, 2, 3]) {|x| @integer = x}
+    @opt.def_option("--range [VAL]", Integer, 1..3) {|x| @range = x}
     @topt = nil
     @opt.def_option("-n") {}
     @opt.def_option("--regexp [REGEXP]", Regexp) {|x| @reopt = x}
     @reopt = nil
     @opt.def_option "--with_underscore=VAL" do |x| @flag = x end
     @opt.def_option "--with-hyphen=VAL" do |x| @flag = x end
+    @opt.def_option("--fallback [VAL]") do |x = "fallback"| @flag = x end
+    @opt.def_option("--lambda [VAL]", &->(x) {@flag = x})
   end
 
   def test_short
@@ -73,4 +79,43 @@ def test_conv
     assert_equal(%w"te.rb", no_error('[ruby-dev:38333]') {@opt.parse!(%w"-T1 te.rb")})
     assert_equal(1, @topt)
   end
+
+  def test_default_argument
+    assert_equal(%w"", no_error {@opt.parse!(%w"--fallback=val1")})
+    assert_equal("val1", @flag)
+    assert_equal(%w"", no_error {@opt.parse!(%w"--fallback val2")})
+    assert_equal("val2", @flag)
+    assert_equal(%w"", no_error {@opt.parse!(%w"--fallback")})
+    assert_equal("fallback", @flag)
+  end
+
+  def test_lambda
+    assert_equal(%w"", no_error {@opt.parse!(%w"--lambda=lambda1")})
+    assert_equal("lambda1", @flag)
+    assert_equal(%w"", no_error {@opt.parse!(%w"--lambda lambda2")})
+    assert_equal("lambda2", @flag)
+    assert_equal(%w"", no_error {@opt.parse!(%w"--lambda")})
+    assert_equal(nil, @flag)
+  end
+
+  def test_enum
+    assert_equal([], no_error {@opt.parse!(%w"--enum=A")})
+    assert_equal(:Alpha, @enum)
+  end
+
+  def test_enum_pair
+    assert_equal([], no_error {@opt.parse!(%w"--enumval=A")})
+    assert_equal(1, @enum)
+  end
+
+  def test_enum_conversion
+    assert_equal([], no_error {@opt.parse!(%w"--integer=1")})
+    assert_equal(1, @integer)
+  end
+
+  def test_enum_range
+    assert_equal([], no_error {@opt.parse!(%w"--range=1")})
+    assert_equal(1, @range)
+    assert_raise(OptionParser::InvalidArgument) {@opt.parse!(%w"--range=4")}
+  end
 end
diff --git a/test/optparse/test_reqarg.rb b/test/optparse/test_reqarg.rb
index d5686d1..31d4fef 100644
--- a/test/optparse/test_reqarg.rb
+++ b/test/optparse/test_reqarg.rb
@@ -6,6 +6,7 @@ def setup
     super
     @opt.def_option "--with_underscore=VAL" do |x| @flag = x end
     @opt.def_option "--with-hyphen=VAL" do |x| @flag = x end
+    @opt.def_option("--lambda=VAL", &->(x) {@flag = x})
   end
 
   class Def1 < TestOptionParser
@@ -81,6 +82,11 @@ def test_hyphenize
     assert_equal("foo4", @flag)
   end
 
+  def test_lambda
+    assert_equal(%w"", no_error {@opt.parse!(%w"--lambda=lambda1")})
+    assert_equal("lambda1", @flag)
+  end
+
   class TestOptionParser::WithPattern < TestOptionParser
     def test_pattern
       pat = num = nil