diff --git a/README.md b/README.md
index 2cca5e8..7d3215e 100644
--- a/README.md
+++ b/README.md
@@ -2,6 +2,10 @@
 
 https://github.com/louisrubet/rpn/ inspired language in ruby
 
+To run REPL locally: `ruby -Ilib bin/rpl`
+
+To run the test suite: `find ./spec/ -name \*.rb -exec ruby -Ilib {} \;`
+
 # TODO-list
   * pseudo filesystem: subdir for variables
   * UI toolkit (based on https://github.com/AndyObtiva/glimmer-dsl-libui ?)
diff --git a/bin/rpl b/bin/rpl
new file mode 100755
index 0000000..720b6be
--- /dev/null
+++ b/bin/rpl
@@ -0,0 +1,51 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+require 'readline'
+
+require 'rpl'
+
+class RplRepl
+  def initialize
+    @interpreter = Rpl.new
+  end
+
+  def run
+    Readline.completion_proc = proc do |s|
+      ( @interpreter.dictionary.words.keys + @interpreter.dictionary.vars.keys ).grep(/^#{Regexp.escape(s)}/)
+    end
+    Readline.completion_append_character = ' '
+
+    loop do
+      input = Readline.readline( ' ', true )
+      break if input.nil? || input == 'quit'
+
+      pp Readline::HISTORY if input == 'history'
+
+      # Remove blank lines from history
+      Readline::HISTORY.pop if input.empty?
+
+      begin
+        @interpreter.run( input )
+      rescue ArgumentError => e
+        p e
+      end
+
+      print_stack
+    end
+  end
+
+  def format_element( elt )
+    @interpreter.stringify( elt )
+  end
+
+  def print_stack
+    stack_size = @interpreter.stack.size
+
+    @interpreter.stack.each_with_index do |elt, i|
+      puts "#{stack_size - i}: #{format_element( elt )}"
+    end
+  end
+end
+
+RplRepl.new.run
diff --git a/lib/rpl.rb b/lib/rpl.rb
new file mode 100644
index 0000000..d06f292
--- /dev/null
+++ b/lib/rpl.rb
@@ -0,0 +1,43 @@
+# frozen_string_literal: true
+
+require 'rpl/interpreter'
+
+require 'rpl/core/branch'
+require 'rpl/core/general'
+require 'rpl/core/mode'
+require 'rpl/core/operations'
+require 'rpl/core/program'
+require 'rpl/core/stack'
+require 'rpl/core/store'
+require 'rpl/core/string'
+require 'rpl/core/test'
+require 'rpl/core/time-date'
+require 'rpl/core/trig'
+require 'rpl/core/logarithm'
+require 'rpl/core/filesystem'
+require 'rpl/core/list'
+
+class Rpl < Interpreter
+  def initialize( stack = [], dictionary = Dictionary.new )
+    super
+
+    populate_dictionary if @dictionary.words.empty?
+  end
+
+  prepend RplLang::Core::Branch
+  prepend RplLang::Core::FileSystem
+  prepend RplLang::Core::General
+  prepend RplLang::Core::List
+  prepend RplLang::Core::Logarithm
+  prepend RplLang::Core::Mode
+  prepend RplLang::Core::Operations
+  prepend RplLang::Core::Program
+  prepend RplLang::Core::Stack
+  prepend RplLang::Core::Store
+  prepend RplLang::Core::String
+  prepend RplLang::Core::Test
+  prepend RplLang::Core::TimeAndDate
+  prepend RplLang::Core::Trig
+
+  def populate_dictionary; end
+end
diff --git a/lib/core/branch.rb b/lib/rpl/core/branch.rb
similarity index 95%
rename from lib/core/branch.rb
rename to lib/rpl/core/branch.rb
index dea644d..4577187 100644
--- a/lib/core/branch.rb
+++ b/lib/rpl/core/branch.rb
@@ -34,8 +34,7 @@ module RplLang
 
                                   run( args[1][:value] )
                                 end
-
-                              end ) # specific
+                              end )
 
         @dictionary.add_word( ['loop'],
                               'Branch',
@@ -49,7 +48,7 @@ module RplLang
 
                                   run( args[2][:value] )
                                 end
-                              end ) # specific
+                              end )
       end
     end
   end
diff --git a/lib/core/filesystem.rb b/lib/rpl/core/filesystem.rb
similarity index 100%
rename from lib/core/filesystem.rb
rename to lib/rpl/core/filesystem.rb
diff --git a/lib/core/general.rb b/lib/rpl/core/general.rb
similarity index 100%
rename from lib/core/general.rb
rename to lib/rpl/core/general.rb
diff --git a/lib/core/list.rb b/lib/rpl/core/list.rb
similarity index 100%
rename from lib/core/list.rb
rename to lib/rpl/core/list.rb
diff --git a/lib/core/logarithm.rb b/lib/rpl/core/logarithm.rb
similarity index 100%
rename from lib/core/logarithm.rb
rename to lib/rpl/core/logarithm.rb
diff --git a/lib/core/mode.rb b/lib/rpl/core/mode.rb
similarity index 99%
rename from lib/core/mode.rb
rename to lib/rpl/core/mode.rb
index 586bbe1..039530a 100644
--- a/lib/core/mode.rb
+++ b/lib/rpl/core/mode.rb
@@ -6,8 +6,6 @@ module RplLang
       def populate_dictionary
         super
 
-
-        # Mode
         @dictionary.add_word( ['prec'],
                               'Mode',
                               '( a -- ) set precision to a',
diff --git a/lib/core/operations.rb b/lib/rpl/core/operations.rb
similarity index 99%
rename from lib/core/operations.rb
rename to lib/rpl/core/operations.rb
index 3040e79..fef436b 100644
--- a/lib/core/operations.rb
+++ b/lib/rpl/core/operations.rb
@@ -385,7 +385,6 @@ module RplLang
         #                       proc do
 
         #                       end )
-
       end
     end
   end
diff --git a/lib/core/program.rb b/lib/rpl/core/program.rb
similarity index 100%
rename from lib/core/program.rb
rename to lib/rpl/core/program.rb
diff --git a/lib/core/stack.rb b/lib/rpl/core/stack.rb
similarity index 99%
rename from lib/core/stack.rb
rename to lib/rpl/core/stack.rb
index d2ecbf9..c1be0f7 100644
--- a/lib/core/stack.rb
+++ b/lib/rpl/core/stack.rb
@@ -124,7 +124,6 @@ module RplLang
                                 end
 
                                 @stack << args[0]
-
                               end )
 
         @dictionary.add_word( ['rolld'],
diff --git a/lib/core/store.rb b/lib/rpl/core/store.rb
similarity index 99%
rename from lib/core/store.rb
rename to lib/rpl/core/store.rb
index 50fd1bf..deaed1e 100644
--- a/lib/core/store.rb
+++ b/lib/rpl/core/store.rb
@@ -60,7 +60,6 @@ module RplLang
   « swap »
   ift
   over rcl + swap sto' )
-
                               end )
 
         @dictionary.add_word( ['sto-'],
@@ -83,7 +82,6 @@ module RplLang
   « swap »
   ift
   over rcl * swap sto' )
-
                               end )
 
         @dictionary.add_word( ['sto÷', 'sto/'],
@@ -95,7 +93,6 @@ module RplLang
   « swap »
   ift
   over rcl swap / swap sto' )
-
                               end )
 
         @dictionary.add_word( ['sneg'],
diff --git a/lib/core/string.rb b/lib/rpl/core/string.rb
similarity index 98%
rename from lib/core/string.rb
rename to lib/rpl/core/string.rb
index 273c06f..0c68d41 100644
--- a/lib/core/string.rb
+++ b/lib/rpl/core/string.rb
@@ -95,7 +95,7 @@ module RplLang
                                 end
 
                                 @stack << result
-                              end ) # specific
+                              end )
 
         @dictionary.add_word( ['split'],
                               'String',
@@ -107,7 +107,7 @@ module RplLang
                                   @stack << { type: :string,
                                               value: elt }
                                 end
-                              end ) # specific
+                              end )
       end
     end
   end
diff --git a/lib/core/test.rb b/lib/rpl/core/test.rb
similarity index 98%
rename from lib/core/test.rb
rename to lib/rpl/core/test.rb
index f9b54f9..1e58fe6 100644
--- a/lib/core/test.rb
+++ b/lib/rpl/core/test.rb
@@ -112,7 +112,7 @@ module RplLang
                               proc do
                                 @stack << { type: :boolean,
                                             value: true }
-                              end ) # specific
+                              end )
 
         @dictionary.add_word( ['false'],
                               'Test',
@@ -120,7 +120,7 @@ module RplLang
                               proc do
                                 @stack << { type: :boolean,
                                             value: false }
-                              end ) # specific
+                              end )
       end
     end
   end
diff --git a/lib/core/time-date.rb b/lib/rpl/core/time-date.rb
similarity index 100%
rename from lib/core/time-date.rb
rename to lib/rpl/core/time-date.rb
diff --git a/lib/core/trig.rb b/lib/rpl/core/trig.rb
similarity index 99%
rename from lib/core/trig.rb
rename to lib/rpl/core/trig.rb
index 0c3da78..11e7403 100644
--- a/lib/core/trig.rb
+++ b/lib/rpl/core/trig.rb
@@ -63,7 +63,6 @@ module RplLang
     ift
   »
   ifte' )
-
                               end )
 
         @dictionary.add_word( ['tan'],
diff --git a/lib/dictionary.rb b/lib/rpl/dictionary.rb
similarity index 100%
rename from lib/dictionary.rb
rename to lib/rpl/dictionary.rb
diff --git a/lib/interpreter.rb b/lib/rpl/interpreter.rb
similarity index 99%
rename from lib/interpreter.rb
rename to lib/rpl/interpreter.rb
index 919aa1c..f693143 100644
--- a/lib/interpreter.rb
+++ b/lib/rpl/interpreter.rb
@@ -2,7 +2,7 @@
 
 require 'bigdecimal/math'
 
-require_relative './dictionary'
+require 'rpl/dictionary'
 
 class Interpreter
   include BigMath
diff --git a/rpl.gemspec b/rpl.gemspec
new file mode 100644
index 0000000..f8c4bb8
--- /dev/null
+++ b/rpl.gemspec
@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+Gem::Specification.new do |s|
+  s.name        = 'rpl'
+  s.version     = '0.1.0'
+  s.summary     = 'Functional Stack Language'
+  s.description = "A language inspired by HP's RPL and https://github.com/louisrubet/rpn/"
+  s.authors     = ['Gwenhael Le Moine']
+  s.email       = 'gwenhael@le-moine.org'
+  s.files       = ['lib/rpl.rb',
+                   'lib/rpl/dictionary.rb',
+                   'lib/rpl/interpreter.rb',
+                   'lib/rpl/core/branch.rb',
+                   'lib/rpl/core/filesystem.rb',
+                   'lib/rpl/core/general.rb',
+                   'lib/rpl/core/list.rb',
+                   'lib/rpl/core/logarithm.rb',
+                   'lib/rpl/core/mode.rb',
+                   'lib/rpl/core/operations.rb',
+                   'lib/rpl/core/program.rb',
+                   'lib/rpl/core/stack.rb',
+                   'lib/rpl/core/store.rb',
+                   'lib/rpl/core/string.rb',
+                   'lib/rpl/core/test.rb',
+                   'lib/rpl/core/time-date.rb',
+                   'lib/rpl/core/trig.rb']
+  s.homepage    = 'https://github.com/gwenhael-le-moine/rpl.rb'
+  s.license     = 'GPL-3.0'
+
+  s.executables << 'rpl'
+
+  s.required_ruby_version = '~> 2.7'
+end
diff --git a/rpl.rb b/rpl.rb
deleted file mode 100644
index d7802e3..0000000
--- a/rpl.rb
+++ /dev/null
@@ -1,90 +0,0 @@
-# frozen_string_literal: true
-
-require 'readline'
-
-require_relative './lib/interpreter'
-
-require_relative './lib/core/branch'
-require_relative './lib/core/general'
-require_relative './lib/core/mode'
-require_relative './lib/core/operations'
-require_relative './lib/core/program'
-require_relative './lib/core/stack'
-require_relative './lib/core/store'
-require_relative './lib/core/string'
-require_relative './lib/core/test'
-require_relative './lib/core/time-date'
-require_relative './lib/core/trig'
-require_relative './lib/core/logarithm'
-require_relative './lib/core/filesystem'
-require_relative './lib/core/list'
-
-class Rpl < Interpreter
-  def initialize( stack = [], dictionary = Dictionary.new )
-    super
-
-    populate_dictionary if @dictionary.words.empty?
-  end
-
-  prepend RplLang::Core::Branch
-  prepend RplLang::Core::FileSystem
-  prepend RplLang::Core::General
-  prepend RplLang::Core::List
-  prepend RplLang::Core::Logarithm
-  prepend RplLang::Core::Mode
-  prepend RplLang::Core::Operations
-  prepend RplLang::Core::Program
-  prepend RplLang::Core::Stack
-  prepend RplLang::Core::Store
-  prepend RplLang::Core::String
-  prepend RplLang::Core::Test
-  prepend RplLang::Core::TimeAndDate
-  prepend RplLang::Core::Trig
-
-  def populate_dictionary; end
-end
-
-class RplRepl
-  def initialize
-    @interpreter = Rpl.new
-  end
-
-  def run
-    Readline.completion_proc = proc do |s|
-      Readline::HISTORY.grep(/^#{Regexp.escape(s)}/)
-    end
-    Readline.completion_append_character = ' '
-
-    loop do
-      input = Readline.readline( ' ', true )
-      break if input.nil? || input == 'quit'
-
-      pp Readline::HISTORY if input == 'history'
-
-      # Remove blank lines from history
-      Readline::HISTORY.pop if input.empty?
-
-      begin
-        @interpreter.run( input )
-      rescue ArgumentError => e
-        p e
-      end
-
-      print_stack
-    end
-  end
-
-  def format_element( elt )
-    @interpreter.stringify( elt )
-  end
-
-  def print_stack
-    stack_size = @interpreter.stack.size
-
-    @interpreter.stack.each_with_index do |elt, i|
-      puts "#{stack_size - i}: #{format_element( elt )}"
-    end
-  end
-end
-
-RplRepl.new.run if __FILE__ == $PROGRAM_NAME
diff --git a/spec/core_spec.rb b/spec/core_spec.rb
index 66ae333..0f6caaf 100644
--- a/spec/core_spec.rb
+++ b/spec/core_spec.rb
@@ -2,7 +2,7 @@
 
 require 'test/unit'
 
-require_relative '../rpl'
+require 'rpl'
 
 class TestParser < Test::Unit::TestCase
   def test_stack_extract
diff --git a/spec/language_branch_spec.rb b/spec/language_branch_spec.rb
index 1506009..33c832b 100644
--- a/spec/language_branch_spec.rb
+++ b/spec/language_branch_spec.rb
@@ -3,7 +3,7 @@
 
 require 'test/unit'
 
-require_relative '../rpl'
+require 'rpl'
 
 class TestLanguageBranch < Test::Unit::TestCase
   def test_loop
diff --git a/spec/language_filesystem_spec.rb b/spec/language_filesystem_spec.rb
index bed3488..a31ce15 100644
--- a/spec/language_filesystem_spec.rb
+++ b/spec/language_filesystem_spec.rb
@@ -3,7 +3,7 @@
 
 require 'test/unit'
 
-require_relative '../rpl'
+require 'rpl'
 
 class TestLanguageFileSystem < Test::Unit::TestCase
   def test_fread
diff --git a/spec/language_operations_spec.rb b/spec/language_operations_spec.rb
index 9adb68d..cdc64af 100644
--- a/spec/language_operations_spec.rb
+++ b/spec/language_operations_spec.rb
@@ -3,7 +3,7 @@
 
 require 'test/unit'
 
-require_relative '../rpl'
+require 'rpl'
 
 class TesttLanguageOperations < Test::Unit::TestCase
   def test_add
diff --git a/spec/language_program_spec.rb b/spec/language_program_spec.rb
index d70e44c..e655366 100644
--- a/spec/language_program_spec.rb
+++ b/spec/language_program_spec.rb
@@ -2,7 +2,7 @@
 
 require 'test/unit'
 
-require_relative '../rpl'
+require 'rpl'
 
 class TestLanguageProgram < Test::Unit::TestCase
   def test_eval
diff --git a/spec/language_stack_spec.rb b/spec/language_stack_spec.rb
index 8e89648..85e7de5 100644
--- a/spec/language_stack_spec.rb
+++ b/spec/language_stack_spec.rb
@@ -3,7 +3,7 @@
 
 require 'test/unit'
 
-require_relative '../rpl'
+require 'rpl'
 
 class TestLanguageStack < Test::Unit::TestCase
   def test_swap
diff --git a/spec/language_store_spec.rb b/spec/language_store_spec.rb
index ddfc8eb..36089e5 100644
--- a/spec/language_store_spec.rb
+++ b/spec/language_store_spec.rb
@@ -2,7 +2,7 @@
 
 require 'test/unit'
 
-require_relative '../rpl'
+require 'rpl'
 
 class TestLanguageProgram < Test::Unit::TestCase
   def test_sto
diff --git a/spec/language_string_spec.rb b/spec/language_string_spec.rb
index d00adc6..44249d9 100644
--- a/spec/language_string_spec.rb
+++ b/spec/language_string_spec.rb
@@ -3,7 +3,7 @@
 
 require 'test/unit'
 
-require_relative '../rpl'
+require 'rpl'
 
 class TestLanguageString < Test::Unit::TestCase
   def test_to_string
diff --git a/spec/language_test_spec.rb b/spec/language_test_spec.rb
index fc26e7d..1bdbcca 100644
--- a/spec/language_test_spec.rb
+++ b/spec/language_test_spec.rb
@@ -3,7 +3,7 @@
 
 require 'test/unit'
 
-require_relative '../rpl'
+require 'rpl'
 
 class TestLanguageTest < Test::Unit::TestCase
   def test_greater_than
diff --git a/spec/language_time-date_spec.rb b/spec/language_time-date_spec.rb
index 089a440..81e669d 100644
--- a/spec/language_time-date_spec.rb
+++ b/spec/language_time-date_spec.rb
@@ -3,7 +3,7 @@
 
 require 'test/unit'
 
-require_relative '../rpl'
+require 'rpl'
 
 class TestLanguageTimeDate < Test::Unit::TestCase
   def test_time
diff --git a/spec/language_trig_spec.rb b/spec/language_trig_spec.rb
index 328a4b6..401432e 100644
--- a/spec/language_trig_spec.rb
+++ b/spec/language_trig_spec.rb
@@ -3,7 +3,7 @@
 
 require 'test/unit'
 
-require_relative '../rpl'
+require 'rpl'
 
 class TesttLanguageOperations < Test::Unit::TestCase
   def test_pi
diff --git a/spec/parser_spec.rb b/spec/parser_spec.rb
index 0865d7d..ed3e2c3 100644
--- a/spec/parser_spec.rb
+++ b/spec/parser_spec.rb
@@ -3,7 +3,7 @@
 
 require 'test/unit'
 
-require_relative '../rpl'
+require 'rpl'
 
 class TestParser < Test::Unit::TestCase
   def test_number