I might have just made up includable, but I like it.

Some times you have written a ruby script (using classes) which does something awesome and it might be nice if other future scripts function could make use of this object class you have just created, while keeping the script in a runnable stand alone state.

This is quite trivial once you realise that $0 is the file that was called on the command line and __FILE__ is the current file.

Available as a gist.

#!/usr/bin/env ruby

class HelloWorld
   def initialize
      @msg = "HelloWorld!"

   def to_s
      return @msg

#Only execute if called directly
#ie other file can require/include and this part will not be executed
# $0 calling file (eneterd at command line)
# __FILE__ This file

if $0 == __FILE__
   hi_world = HelloWorld.new
   puts hi_world