Love the idea.  Where do I find "tap"


C:/Ruby/lib/ruby/gems/1.8/gems/col-1.0.1/lib/col.rb:101:in `result': 
undefined method `tap' for "":String (NoMethodError)
     from C:/Ruby/lib/ruby/gems/1.8/gems/col-1.0.1/lib/col.rb:54:in `fmt'
     from C:/Ruby/lib/ruby/gems/1.8/gems/col-1.0.1/lib/col.rb:71:in 
`method_missing'


101    String.new.tap { |str|
102     @strings.zip(@format_spec).each do |string, spec|
103      d = decorated_string(string, spec)
104      str << d
105     end
106    }