Duplicate the spec for diferent ruby versions

This spec returns 4 on MRI 1.8.7p358 and 2 on MRI 1.9.3p194.

spec/ruby/language/block_spec.rb

@@ -507,17 +507,21 @@
 
   describe "arguments with _" do
 
-    it "extracts arguments with _" do
-      @y.m([[1, 2, 3], 4]) { |(_, a, _), _| a }.should == 2
-    end
-
     ruby_version_is ""..."1.9" do
+      it "extracts arguments with _" do
+        @y.m([[1, 2, 3], 4]) { |(_, a, _), _| a }.should == 4
+      end
+
       it "assigns the last variable named" do
         @y.m(1, 2) { |_, _| _ }.should == 2
       end
     end
 
     ruby_version_is "1.9" do
+      it "extracts arguments with _" do
+        @y.m([[1, 2, 3], 4]) { |(_, a, _), _| a }.should == 2
+      end
+
       it "assigns the first variable named" do
         @y.m(1, 2) { |_, _| _ }.should == 1
       end