diff --git a/ext/ripper/tools/dsl.rb b/ext/ripper/tools/dsl.rb
index 3e368813e5..d0002d1ec3 100644
--- a/ext/ripper/tools/dsl.rb
+++ b/ext/ripper/tools/dsl.rb
@@ -20,6 +20,12 @@ class DSL
   NAME_PATTERN = /(?>\$|\d+|[a-zA-Z_][a-zA-Z0-9_]*|\[[a-zA-Z_.][-a-zA-Z0-9_.]*\])(?>(?:\.|->)[a-zA-Z_][a-zA-Z0-9_]*)*/.source
   NOT_REF_PATTERN = /(?>\#.*|[^\"$@]*|"(?>\\.|[^\"])*")/.source
 
+  def self.line?(line, lineno = nil)
+    if %r</\*% *ripper(?:\[(.*?)\])?: *(.*?) *%\*/> =~ line
+      new($2, $1&.split(",") || [], lineno)
+    end
+  end
+
   def initialize(code, options, lineno = nil)
     @lineno = lineno
     @events = {}
diff --git a/ext/ripper/tools/generate.rb b/ext/ripper/tools/generate.rb
index 27aa53bce0..92ced37f04 100644
--- a/ext/ripper/tools/generate.rb
+++ b/ext/ripper/tools/generate.rb
@@ -167,15 +167,13 @@ require_relative "dsl"
 def read_ids1_with_locations(path)
   h = {}
   File.open(path) {|f|
-    f.each.with_index(1) do |line, i|
+    f.each do |line|
       next if /\A\#\s*define\s+dispatch/ =~ line
       next if /ripper_dispatch/ =~ line
       line.scan(/\bdispatch(\d)\((\w+)/) do |arity, event|
         (h[event] ||= []).push [f.lineno, arity.to_i]
       end
-      if line =~ %r</\*% *ripper(?:\[(.*?)\])?: *(.*?) *%\*/>
-        gen = DSL.new($2, ($1 || "").split(","), i)
-        gen.generate
+      if gen = DSL.line?(line, f.lineno)
         gen.events.each do |event, arity|
           (h[event] ||= []).push [f.lineno, arity.to_i]
         end
diff --git a/ext/ripper/tools/preproc.rb b/ext/ripper/tools/preproc.rb
index 25cd46e1be..a92be93d5b 100644
--- a/ext/ripper/tools/preproc.rb
+++ b/ext/ripper/tools/preproc.rb
@@ -53,50 +53,48 @@ end
 
 require_relative 'dsl'
 
-RIPPER_CODE_PATTERN = %r</\*% *ripper(?:\[(.*?)\])?: *(.*?) *%\*/>
+def generate_line(f, out)
+  while line = f.gets
+    case
+    when gen = DSL.line?(line)
+      out << gen.generate << "\n"
+    when line.start_with?("%%")
+      out << "%%\n"
+      break
+    else
+      out << yield(line)
+    end
+  end
+end
 
 def prelude(f, out)
   @exprs = {}
-  while line = f.gets
-    case line
-    when /\A%%/
-      out << "%%\n"
-      return
-    when RIPPER_CODE_PATTERN # %rule actions may contain /*% ripper: ... %*/ DSL
-      out << DSL.new($2, ($1 || "").split(",")).generate << "\n"
-      next
-    else
-      if (/^enum lex_state_(?:bits|e) \{/ =~ line)..(/^\}/ =~ line)
-        case line
-        when /^\s*(EXPR_\w+),\s+\/\*(.+)\*\//
-          @exprs[$1.chomp("_bit")] = $2.strip
-        when /^\s*(EXPR_\w+)\s+=\s+(.+)$/
-          name = $1
-          val = $2.chomp(",")
-          @exprs[name] = "equals to " + (val.start_with?("(") ? "<tt>#{val}</tt>" : "+#{val}+")
-        end
+  generate_line(f, out) do |line|
+    if (/^enum lex_state_(?:bits|e) \{/ =~ line)..(/^\}/ =~ line)
+      case line
+      when /^\s*(EXPR_\w+),\s+\/\*(.+)\*\//
+        @exprs[$1.chomp("_bit")] = $2.strip
+      when /^\s*(EXPR_\w+)\s+=\s+(.+)$/
+        name = $1
+        val = $2.chomp(",")
+        @exprs[name] = "equals to " + (val.start_with?("(") ? "<tt>#{val}</tt>" : "+#{val}+")
       end
     end
-    out << line
+    line
   end
 end
 
 def grammar(f, out)
-  while line = f.gets
+  generate_line(f, out) do |line|
     case line
-    when RIPPER_CODE_PATTERN
-      out << DSL.new($2, ($1 || "").split(",")).generate << "\n"
     when %r</\*%%%\*/>
-      out << "#if 0\n"
+      "#if 0\n"
     when %r</\*%>
-      out << "#endif\n"
+      "#endif\n"
     when %r<%\*/>
-      out << "\n"
-    when /\A%%/
-      out << "%%\n"
-      return
+      "\n"
     else
-      out << line
+      line
     end
   end
 end