diff --git a/lib/imbecile.rb b/lib/imbecile.rb
index 5a7e113..08dba08 100644
--- a/lib/imbecile.rb
+++ b/lib/imbecile.rb
@@ -1,6 +1,7 @@
 require_relative "imbecile/cli"
 require_relative "imbecile/grammar"
 require_relative "imbecile/regex"
+require_relative "imbecile/regex/unit"
 require_relative "imbecile/version"
 require "erb"
 
diff --git a/lib/imbecile/regex.rb b/lib/imbecile/regex.rb
index e46fe88..0eede93 100644
--- a/lib/imbecile/regex.rb
+++ b/lib/imbecile/regex.rb
@@ -14,204 +14,7 @@ module Imbecile
     end
 
     def initialize(pattern)
-      @pattern = pattern.dup
-      parse
-    end
-
-    private
-
-    class Unit
-    end
-
-    class SequenceUnit < Unit
-      attr_accessor :units
-      def initialize
-        @units = []
-      end
-      def method_missing(*args)
-        @units.__send__(*args)
-      end
-    end
-
-    class AlternatesUnit < Unit
-      attr_accessor :alternates
-      attr_accessor :negate
-      def initialize
-        @alternates = []
-        @negate = false
-      end
-      def new_alternate!
-        @alternates << SequenceUnit.new
-      end
-      def append_alternate(unit)
-        @alternates << unit
-      end
-      def <<(unit)
-        new_alternate! if @alternates.empty?
-        @alternates[-1] << unit
-      end
-      def last_unit
-        new_alternate! if @alternates.empty?
-        @alternates[-1][-1]
-      end
-      def replace_last!(new_unit)
-        @alternates[-1][-1] = new_unit
-      end
-    end
-
-    class CharacterUnit < Unit
-      attr_accessor :code_point
-      def initialize(c)
-        @code_point = c.ord
-      end
-    end
-
-    class CharacterRangeUnit < Unit
-      attr_accessor :start_code_point
-      attr_accessor :end_code_point
-      def initialize(c1, c2)
-        @start_code_point = c1.ord
-        @end_code_point = c2.ord
-      end
-    end
-
-    class MultiplicityUnit < Unit
-      attr_accessor :unit
-      attr_accessor :min_count
-      attr_accessor :max_count
-      def initialize(unit, min_count, max_count)
-        @unit = unit
-        @min_count = min_count
-        @max_count = max_count
-      end
-    end
-
-    def parse
-      @unit = parse_alternates
-      if @pattern != ""
-        raise "Invalid pattern: #{@pattern}"
-      end
-    end
-
-    def parse_alternates
-      au = AlternatesUnit.new
-      while @pattern != ""
-        c = @pattern[0]
-        return au if c == ")"
-        @pattern.slice!(0)
-        case c
-        when "["
-          au << parse_character_class
-        when "("
-          au << parse_group
-        when "*", "+", "?", "{"
-          if last_unit = au.last_unit
-            case c
-            when "*"
-              min_count, max_count = 0, nil
-            when "+"
-              min_count, max_count = 1, nil
-            when "?"
-              min_count, max_count = 0, 1
-            when "{"
-              min_count, max_count = parse_curly_count
-            end
-            mu = MultiplicityUnit.new(last_unit, min_count, max_count)
-            au.replace_last!(mu)
-          else
-            raise Error.new("#{c} follows nothing")
-          end
-        when "|"
-          au.new_alternate!
-        when "\\"
-          au << parse_backslash
-        else
-          au << CharacterUnit.new(c)
-        end
-      end
-      au
-    end
-
-    def parse_group
-      au = parse_alternates
-      if @pattern[0] != ")"
-        raise Error.new("Unterminated group in pattern")
-      end
-      @pattern.slice!(0)
-      au
-    end
-
-    def parse_character_class
-      au = AlternatesUnit.new
-      index = 0
-      loop do
-        if @pattern == ""
-          raise Error.new("Unterminated character class")
-        end
-        c = @pattern.slice!(0)
-        if c == "]"
-          break
-        elsif c == "^" && index == 0
-          au.negate = true
-        elsif c == "-" && (index == 0 || @pattern[0] == "]")
-          au.append_alternate(CharacterUnit.new(c))
-        elsif c == "\\"
-          au.append_alternate(parse_backslash)
-        elsif c == "-" && @pattern[0] != "]"
-          begin_cu = au.last_unit
-          unless begin_cu.is_a?(CharacterUnit)
-            raise Error.new("Character range must be between single characters")
-          end
-          if @pattern[0] == "\\"
-            @pattern.slice!(0)
-            end_cu = parse_backslash
-            unless end_cu.is_a?(CharacterUnit)
-              raise Error.new("Character range must be between single characters")
-            end
-            end_code_point = end_cu.code_point
-          else
-            end_code_point = @pattern[0].ord
-            @pattern.slice!(0)
-          end
-          cru = CharacterRangeUnit.new(begin_cu.code_point, end_code_point)
-          au.replace_last!(cru)
-        else
-          au.append_alternate(CharacterUnit.new(c))
-        end
-        index += 1
-      end
-      au
-    end
-
-    def parse_curly_count
-      if @pattern =~ /^(\d+)(?:,(\d+))?\}(.*)$/
-        min_count = $1.to_i
-        max_count = nil
-        if $2 != ""
-          max_count = $2.to_i
-          if max_count < min_count
-            raise Error.new("Maximum repetition count cannot be less than minimum repetition count")
-          end
-        end
-        @pattern = $3
-        [min_count, max_count]
-      else
-        raise Error.new("Unexpected match count at #{@pattern}")
-      end
-    end
-
-    def parse_backslash
-      if @pattern == ""
-        raise Error.new("Error: unfollowed \\")
-      else
-        c = @pattern.slice!(0)
-        case c
-        when "d"
-          CharacterRangeUnit.new("0", "9")
-        else
-          CharacterUnit.new(c)
-        end
-      end
+      @unit = Unit.new(pattern)
     end
 
   end
diff --git a/lib/imbecile/regex/unit.rb b/lib/imbecile/regex/unit.rb
new file mode 100644
index 0000000..9dce5c6
--- /dev/null
+++ b/lib/imbecile/regex/unit.rb
@@ -0,0 +1,203 @@
+module Imbecile
+  class Regex
+
+    class Unit
+
+      class SequenceUnit < Unit
+        attr_accessor :units
+        def initialize
+          @units = []
+        end
+        def method_missing(*args)
+          @units.__send__(*args)
+        end
+      end
+
+      class AlternatesUnit < Unit
+        attr_accessor :alternates
+        attr_accessor :negate
+        def initialize
+          @alternates = []
+          @negate = false
+        end
+        def new_alternate!
+          @alternates << SequenceUnit.new
+        end
+        def append_alternate(unit)
+          @alternates << unit
+        end
+        def <<(unit)
+          new_alternate! if @alternates.empty?
+          @alternates[-1] << unit
+        end
+        def last_unit
+          new_alternate! if @alternates.empty?
+          @alternates[-1][-1]
+        end
+        def replace_last!(new_unit)
+          @alternates[-1][-1] = new_unit
+        end
+      end
+
+      class CharacterUnit < Unit
+        attr_accessor :code_point
+        def initialize(c)
+          @code_point = c.ord
+        end
+      end
+
+      class CharacterRangeUnit < Unit
+        attr_accessor :start_code_point
+        attr_accessor :end_code_point
+        def initialize(c1, c2)
+          @start_code_point = c1.ord
+          @end_code_point = c2.ord
+        end
+      end
+
+      class MultiplicityUnit < Unit
+        attr_accessor :unit
+        attr_accessor :min_count
+        attr_accessor :max_count
+        def initialize(unit, min_count, max_count)
+          @unit = unit
+          @min_count = min_count
+          @max_count = max_count
+        end
+      end
+
+      def initialize(pattern)
+        @pattern = pattern.dup
+        @unit = parse_alternates
+        if @pattern != ""
+          raise "Invalid pattern: #{@pattern}"
+        end
+      end
+
+      private
+
+      def parse_alternates
+        au = AlternatesUnit.new
+        while @pattern != ""
+          c = @pattern[0]
+          return au if c == ")"
+          @pattern.slice!(0)
+          case c
+          when "["
+            au << parse_character_class
+          when "("
+            au << parse_group
+          when "*", "+", "?", "{"
+            if last_unit = au.last_unit
+              case c
+              when "*"
+                min_count, max_count = 0, nil
+              when "+"
+                min_count, max_count = 1, nil
+              when "?"
+                min_count, max_count = 0, 1
+              when "{"
+                min_count, max_count = parse_curly_count
+              end
+              mu = MultiplicityUnit.new(last_unit, min_count, max_count)
+              au.replace_last!(mu)
+            else
+              raise Error.new("#{c} follows nothing")
+            end
+          when "|"
+            au.new_alternate!
+          when "\\"
+            au << parse_backslash
+          else
+            au << CharacterUnit.new(c)
+          end
+        end
+        au
+      end
+
+      def parse_group
+        au = parse_alternates
+        if @pattern[0] != ")"
+          raise Error.new("Unterminated group in pattern")
+        end
+        @pattern.slice!(0)
+        au
+      end
+
+      def parse_character_class
+        au = AlternatesUnit.new
+        index = 0
+        loop do
+          if @pattern == ""
+            raise Error.new("Unterminated character class")
+          end
+          c = @pattern.slice!(0)
+          if c == "]"
+            break
+          elsif c == "^" && index == 0
+            au.negate = true
+          elsif c == "-" && (index == 0 || @pattern[0] == "]")
+            au.append_alternate(CharacterUnit.new(c))
+          elsif c == "\\"
+            au.append_alternate(parse_backslash)
+          elsif c == "-" && @pattern[0] != "]"
+            begin_cu = au.last_unit
+            unless begin_cu.is_a?(CharacterUnit)
+              raise Error.new("Character range must be between single characters")
+            end
+            if @pattern[0] == "\\"
+              @pattern.slice!(0)
+              end_cu = parse_backslash
+              unless end_cu.is_a?(CharacterUnit)
+                raise Error.new("Character range must be between single characters")
+              end
+              end_code_point = end_cu.code_point
+            else
+              end_code_point = @pattern[0].ord
+              @pattern.slice!(0)
+            end
+            cru = CharacterRangeUnit.new(begin_cu.code_point, end_code_point)
+            au.replace_last!(cru)
+          else
+            au.append_alternate(CharacterUnit.new(c))
+          end
+          index += 1
+        end
+        au
+      end
+
+      def parse_curly_count
+        if @pattern =~ /^(\d+)(?:,(\d+))?\}(.*)$/
+          min_count = $1.to_i
+          max_count = nil
+          if $2 != ""
+            max_count = $2.to_i
+            if max_count < min_count
+              raise Error.new("Maximum repetition count cannot be less than minimum repetition count")
+            end
+          end
+          @pattern = $3
+          [min_count, max_count]
+        else
+          raise Error.new("Unexpected match count at #{@pattern}")
+        end
+      end
+
+      def parse_backslash
+        if @pattern == ""
+          raise Error.new("Error: unfollowed \\")
+        else
+          c = @pattern.slice!(0)
+          case c
+          when "d"
+            CharacterRangeUnit.new("0", "9")
+          else
+            CharacterUnit.new(c)
+          end
+        end
+      end
+
+    end
+
+  end
+end