replacer.rb

require 'hpricot'
require 'coderay'
require 'rdiscount'
#open the file in markdown
f = File.open "tmp.markdown"
#generate html with rdiscount
md = RDiscount.new f.read
#parse it with hpricot and be magical
d = Hpricot md.to_html
d.search "pre" do |code| 
    lang = ""
    lines = code.innerText.split "\n"
    lines.each do |line|
        if line[0..2] == "@@@"
            lang = line.gsub "@@@", '' 
            break
        end
    end
    #ok, we have the lang, now, color it
    newhtml = Hpricot CodeRay.scan(lines[1..-1].join("\n"), lang.to_sym).div :line_numbers => :inline
    d.replace_child code, newhtml
end

fn = File.new "tmp_coded.html", 'w'
fn.write d.to_s
fn.close