diff --git a/Gemfile b/Gemfile
index 7cb7a54..e734a98 100644
--- a/Gemfile
+++ b/Gemfile
@@ -2,6 +2,9 @@ ruby "2.7.2"
 
 source "https://rubygems.org"
 
+# Command-line argument parsing
+gem "dry-cli"
+
 # Building
 gem "overcommit"
 gem "rubocop", require: false
diff --git a/Gemfile.lock b/Gemfile.lock
index f857b4b..ffae583 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -5,6 +5,9 @@ GEM
     byebug (11.1.3)
     childprocess (4.0.0)
     coderay (1.1.3)
+    concurrent-ruby (1.1.8)
+    dry-cli (0.6.0)
+      concurrent-ruby (~> 1.0)
     iniparse (1.5.0)
     io-console (0.5.7)
     irb (1.3.2)
@@ -54,6 +57,7 @@ PLATFORMS
   ruby
 
 DEPENDENCIES
+  dry-cli
   irb
   kramdown
   overcommit
diff --git a/Makefile b/Makefile
index 2da5e11..30aa42e 100644
--- a/Makefile
+++ b/Makefile
@@ -12,7 +12,7 @@ lint: rubocop
 
 
 verify-specs: bundle
-	bin/stone --debug verify docs/specs/*.md
+	bin/stone verify --debug docs/specs/*.md
 
 setup-overcommit: .git/hooks/overcommit-hook
 
diff --git a/README.md b/README.md
index 6a0ad9a..4b05eb7 100644
--- a/README.md
+++ b/README.md
@@ -53,10 +53,11 @@ Running
 
 Binaries are located in the `bin` directory:
 
-* `stone` - the main executable
-    * `stone eval` - output the result of each top-level expression
-    * `stone repl` - accept manual input, and show the result of each line
-    * `stone verify` - check that results of top-level expressions match expectations in comments
+* `stone`
+    * `stone eval` - Output the result of each top-level expression (non-interactive REPL)
+    * `stone repl` - Accept interactive manual input, and show the result of each top-level expression
+    * `stone verify` - Verify that results of top-level expressions match expectations in comments
+    * `stone parse` - Output the parse tree
 
 
 License
diff --git a/src/stone/cli.rb b/src/stone/cli.rb
index 77280f3..0d444fb 100644
--- a/src/stone/cli.rb
+++ b/src/stone/cli.rb
@@ -1,168 +1,20 @@
-require "extensions/argf"
-require "extensions/class"
-
-require "stone/version"
-require "stone/verification/suite"
-require "stone/top"
-require "stone/ast/error"
-
-# Load all the sub-languages, then determine the highest-level sub-language (it'll have the most ancestors).
-Dir[File.join(__dir__, "language", "*.rb")].sort.each do |file|
-  require file
-end
-DEFAULT_LANGUAGE = Stone::Language::Base.descendants.max_by { |lang| lang.ancestors.size }
-
-require "readline"
-require "kramdown"
+require "dry/cli"
 
 
 module Stone
+  module CLI
 
-  class CLI
+    extend Dry::CLI::Registry
 
     def self.run
-      new.run
-    end
-
-    def run
-      if options.include?("--version")
-        puts "Stone version #{Stone::VERSION}"
-        exit 0
-      elsif self.respond_to?("run_#{subcommand}", true)
-        __send__("run_#{subcommand}")
-        exit 0
-      else
-        puts "Don't know the '#{subcommand}' subcommand."
-        exit 1
-      end
-    end
-
-    private def language
-      @language ||= DEFAULT_LANGUAGE.new
-    end
-
-    private def run_parse
-      each_input_file do |input|
-        puts language.parse(input)
-      rescue Parslet::ParseFailed => e
-        puts e.parse_failure_cause.ascii_tree
-        exit 1
-      end
-    end
-
-    private def run_eval
-      each_input_file do |input|
-        top_context = Stone::Top.context
-        puts language.ast(input).map{ |node|
-          node.evaluate(top_context)
-        }.compact
-      rescue Parslet::ParseFailed => e
-        puts e.parse_failure_cause.ascii_tree
-        exit 1
-      end
-    end
-
-    private def run_repl
-      puts "Stone REPL"
-      while (input = Readline.readline("#> ", true))
-        repl_1_line(input, top_context)
-      end
-    end
-
-    private def repl_1_line(line, context)
-      ast = language.ast(line, single_line: true)
-      case result = ast.evaluate(context)
-      when AST::Error
-        puts "#! #{result}"
-      when AST::Value
-        puts "#= #{result}"
-      end
-    rescue Parslet::ParseFailed => e
-      puts e.parse_failure_cause.ascii_tree
-    end
-
-    private def run_verify
-      suite = Stone::Verification::Suite.new(debug: debug_option?)
-      each_input_file do |input|
-        suite.run(input) do
-          language.ast(input)
-        rescue Parslet::ParseFailed => e
-          suite.add_failure(input, Stone::AST::Error.new("ParseError", e.parse_failure_cause))
-          []
-        end
-      end
-      suite.complete
-    end
-
-    private def options # rubocop:disable Metrics/AbcSize, Metrics/MethodLength
-      return @options if @options
-      @options = []
-      while ARGV[0] =~ /^--/
-        @options << ARGV[0]
-        ARGV.shift
-        # TODO: I should really use an options-parsing library here.
-        if @options.last == "--grammar" # rubocop:disable Style/Next
-          grammar = ARGV[0].capitalize
-          if Stone::Language.const_defined?(grammar.to_sym)
-            @language = Stone::Language.const_get(grammar.to_sym).new
-          else
-            puts "Don't know the #{grammar} sub-language."
-            exit 1
-          end
-          ARGV.shift
-        end
-      end
-      @options
-    end
-
-    private def subcommand
-      return @subcommand if @subcommand
-      options # Global options come before subcommands, so we have to look for them in ARGV first.
-      @subcommand = ARGV[0]
-      ARGV.shift
-      @subcommand
-    end
-
-    private def each_input_file(&block)
-      ARGF.each_file do |file|
-        if ARGF.filename.end_with?(".md") || (ARGF.filename == "-" && markdown_option?)
-          markdown_code_blocks(file).each do |code_block|
-            block.call(code_block)
-          end
-        else
-          input = file.read
-          block.call(input.end_with?("\n") ? input : input << "\n")
-        end
-      end
-    end
-
-    private def markdown_code_blocks(file)
-      markdown = Kramdown::Document.new(file.read)
-      markdown.root.children.select{ |e| e.type == :codeblock && e.options[:lang] == "stone" }.map(&:value)
-    end
-
-    private def parse(input)
-      parser.parse("#{input}\n", reporter: Parslet::ErrorReporter::Contextual.new)
-    end
-
-    private def transform(parse_tree)
-      transformer = Stone::Transform.new
-      ast = transformer.apply(parse_tree)
-      ast.respond_to?(:compact) ? ast.compact : ast
-    end
-
-    private def markdown_option?
-      options.include?("--markdown")
-    end
-
-    private def debug_option?
-      options.include?("--debug")
-    end
-
-    private def top_context
-      @top_context ||= Stone::Top.context
+      Dry::CLI.new(self).call
     end
 
   end
+end
 
+
+# Load all the sub-commands.
+Dir[File.join(__dir__, "cli", "*.rb")].sort.each do |file|
+  require file
 end
diff --git a/src/stone/cli/command.rb b/src/stone/cli/command.rb
new file mode 100644
index 0000000..68c4108
--- /dev/null
+++ b/src/stone/cli/command.rb
@@ -0,0 +1,48 @@
+require "dry/cli"
+require "kramdown"
+
+require "stone/language"
+
+
+module Stone
+  module CLI
+
+    class Command < Dry::CLI::Command
+
+      private def each_input_file(files, markdown: false, &block) # rubocop:disable Metrics/MethodLength
+        files.each do |filename|
+          file = File.open(filename) # TODO: Handle `-` and handle missing files.
+          if filename.end_with?(".md") || (filename == "-" && markdown)
+            markdown_code_blocks(file).each do |code_block|
+              block.call(code_block)
+            end
+          else
+            input = file.read
+            block.call(input.end_with?("\n") ? input : input << "\n")
+          end
+        end
+      end
+
+      private def language
+        @language ||= Stone::Language::DEFAULT.new
+      end
+
+      private def markdown_code_blocks(file)
+        markdown = Kramdown::Document.new(file.read)
+        markdown.root.children.select{ |e| e.type == :codeblock && e.options[:lang] == "stone" }.map(&:value)
+      end
+
+      private def parse(input)
+        parser.parse("#{input}\n", reporter: Parslet::ErrorReporter::Contextual.new)
+      end
+
+      private def transform(parse_tree)
+        transformer = Stone::Transform.new
+        ast = transformer.apply(parse_tree)
+        ast.respond_to?(:compact) ? ast.compact : ast
+      end
+
+    end
+
+  end
+end
diff --git a/src/stone/cli/eval.rb b/src/stone/cli/eval.rb
new file mode 100644
index 0000000..1a67ee5
--- /dev/null
+++ b/src/stone/cli/eval.rb
@@ -0,0 +1,33 @@
+require "parslet"
+
+require "stone/cli/command"
+require "stone/top"
+
+
+module Stone
+  module CLI
+
+    class Eval < Stone::CLI::Command
+
+      desc "Output the result of each top-level expression (non-interactive REPL)"
+      argument :source_files, type: :array, required: true, desc: "Source files"
+      option :markdown, type: :boolean, default: false
+
+      def call(source_files:, markdown:, **_args)
+        each_input_file(source_files, markdown: markdown) do |input|
+          top_context = Stone::Top.context
+          puts language.ast(input).map{ |node|
+            node.evaluate(top_context)
+          }.compact
+        rescue Parslet::ParseFailed => e
+          puts e.parse_failure_cause.ascii_tree
+          exit 1
+        end
+      end
+
+    end
+
+    register "eval", Eval
+
+  end
+end
diff --git a/src/stone/cli/parse.rb b/src/stone/cli/parse.rb
new file mode 100644
index 0000000..73a1f70
--- /dev/null
+++ b/src/stone/cli/parse.rb
@@ -0,0 +1,29 @@
+require "parslet"
+
+require "stone/cli/command"
+
+
+module Stone
+  module CLI
+
+    class Parse < Stone::CLI::Command
+
+      desc "Output the parse tree"
+      argument :source_files, type: :array, required: true, desc: "Source files"
+      option :markdown, type: :boolean, default: false
+
+      def call(source_files:, markdown:, **_args)
+        each_input_file(source_files, markdown: markdown) do |input|
+          puts language.parse(input)
+        rescue Parslet::ParseFailed => e
+          puts e.parse_failure_cause.ascii_tree
+          exit 1
+        end
+      end
+
+    end
+
+    register "parse", Parse
+
+  end
+end
diff --git a/src/stone/cli/repl.rb b/src/stone/cli/repl.rb
new file mode 100644
index 0000000..39afd1f
--- /dev/null
+++ b/src/stone/cli/repl.rb
@@ -0,0 +1,43 @@
+require "readline"
+require "parslet"
+
+require "stone/cli/command"
+require "stone/top"
+
+
+module Stone
+  module CLI
+
+    class REPL < Stone::CLI::Command
+
+      desc "Accept interactive manual input, and show the result of each top-level expression"
+
+      def call(**_args)
+        puts "Stone REPL"
+        while (input = Readline.readline("#> ", true))
+          repl_1_line(input, top_context)
+        end
+      end
+
+      private def repl_1_line(line, context)
+        ast = language.ast(line, single_line: true)
+        case result = ast.evaluate(context)
+        when AST::Error
+          puts "#! #{result}"
+        when AST::Value
+          puts "#= #{result}"
+        end
+      rescue Parslet::ParseFailed => e
+        puts e.parse_failure_cause.ascii_tree
+      end
+
+      private def top_context
+        @top_context ||= Stone::Top.context
+      end
+
+    end
+
+    register "repl", REPL
+
+  end
+end
diff --git a/src/stone/cli/verify.rb b/src/stone/cli/verify.rb
new file mode 100644
index 0000000..c1ec90f
--- /dev/null
+++ b/src/stone/cli/verify.rb
@@ -0,0 +1,35 @@
+require "parslet"
+
+require "stone/cli/command"
+require "stone/verification/suite"
+
+
+module Stone
+  module CLI
+
+    class Verify < Stone::CLI::Command
+
+      desc "Verify that results of top-level expressions match expectations in comments"
+      argument :source_files, type: :array, required: true, desc: "Source files"
+      option :debug, type: :boolean, default: false
+      option :markdown, type: :boolean, default: false
+
+      def call(source_files:, debug:, markdown:, **_args)
+        suite = Stone::Verification::Suite.new(debug: debug)
+
+        each_input_file(source_files, markdown: markdown) do |input|
+          suite.run(input) do
+            language.ast(input)
+          rescue Parslet::ParseFailed => e
+            suite.add_failure(input, Stone::AST::Error.new("ParseError", e.parse_failure_cause))
+            []
+          end
+        end
+        suite.complete
+      end
+    end
+
+    register "verify", Verify
+
+  end
+end
diff --git a/src/stone/cli/version.rb b/src/stone/cli/version.rb
new file mode 100644
index 0000000..5fea1a0
--- /dev/null
+++ b/src/stone/cli/version.rb
@@ -0,0 +1,21 @@
+require "stone/cli/command"
+require "stone/version"
+
+
+module Stone
+  module CLI
+
+    class Version < Stone::CLI::Command
+
+      desc "Print version"
+
+      def call(*)
+        puts "Stone version #{Stone::VERSION}"
+      end
+
+    end
+
+    register "version", Version, aliases: ["--version", "-v"]
+
+  end
+end
diff --git a/src/stone/language.rb b/src/stone/language.rb
new file mode 100644
index 0000000..3d0f147
--- /dev/null
+++ b/src/stone/language.rb
@@ -0,0 +1,16 @@
+# Load all the sub-languages.
+Dir[File.join(__dir__, "language", "*.rb")].sort.each do |file|
+  require file
+end
+
+require "extensions/class"
+
+
+module Stone
+  module Language
+
+    # Determine the highest-level language (it'll have the most ancestors).
+    DEFAULT = Stone::Language::Base.descendants.max_by { |lang| lang.ancestors.size }
+
+  end
+end
diff --git a/src/stone/language/base.rb b/src/stone/language/base.rb
index 55e1369..47dcf01 100644
--- a/src/stone/language/base.rb
+++ b/src/stone/language/base.rb
@@ -1,5 +1,4 @@
 require "extensions/module"
-require "extensions/enumerable"
 
 require "stone/ast/base"