etanni.rb

class Etanni
  SEPARATOR = "E69t116A65n110N78i105S83e101P80a97R82a97T84o111R82"
  CHOMP = "<<#{SEPARATOR}.chomp!"
  START = "\n_out_ << #{CHOMP}\n"
  STOP = "\n#{SEPARATOR}\n"
  REPLACEMENT = "#{STOP}\\1#{START}"

  def initialize(template, filename = '<Etanni>')
    @template = template
    @filename = filename
    compile
  end

  def compile(filename = @filename)
    temp = @template.strip
    temp.gsub!(/<\?r\s+(.*?)\s+\?>/m, REPLACEMENT)
    @compiled = eval("Proc.new{ _out_ = [#{CHOMP}]\n#{temp}#{STOP}_out_.join }",
      nil, @filename)
  end

  def result(instance, filename = @filename)
    instance.instance_eval(&@compiled)
  end
end

etanni = Etanni.new('Hello, #{name}')
p etanni.result(Struct.new(:name).new('manveru'))