Different ways to bind procs, depending on ruby version and whether you work with ActiveSupport.

gistfile1.rb

class A
  LAMB1 = lambda{ do_it }
  LAMB2 = proc{ do_it }

  def do_it
    puts "AAA"
  end
end

class B
  def do_it
    puts "BBB"
  end

  def test_1
    instance_eval(&A::LAMB1)
  end

  def test_2
    instance_eval(&A::LAMB2)
  end

  def test_3
    A::LAMB1.bind(self).call
  end
end

b = B.new

begin
  # will work in ruby 1.8.7 only
  b.test_1
rescue Exception => e
  puts e
end

begin
  # will work in ruby 1.8.7 and 1.9.3
  b.test_2
rescue Exception => e
  puts e
end

begin
  # will work IN RAILS in ruby 1.8.7 and 1.9.3.
  b.test_3
rescue Exception => e
  puts e
end