core_ext_with.rb

module Kernel
  def with(object, &block)
    object.instance_eval &block
  end
end

# Simple way to use it
with "Ruby Rocks!" do
  puts self
  puts size
end

# More verbose way of using it
with "Ruby" do |s1|
  with "Rocks!" do |s2|
    puts "#{s1} #{s2}"
  end
end