Detectando erros de sintaxe no preview

app/controllers/wiki_controller.rb

@@ -112,7 +112,11 @@ class WikiController < ApplicationController
 
 	def preview
 		@text = params[:text]
+		begin
 			render :text => BlueCloth.new(@text).to_html
+		rescue
+			render :text => $!.to_s.gsub(">", "&gt;").gsub("<", "&lt;")
+		end
 	end
 
 	def diff