I'm trying to use the align_center method for the String class and it 
never works as shown below.  Any ideas?

http://nano.rubyforge.org/doc/classes/String.html

Code:
    k = String.new("hello").align_center(14)

Error:
    c:/cronjobs/test.rb:1: undefined method `align_center' for 
"hello":String (NoMethodError)

Thanks,
Charles