# Check to see whether it is defined
puts "var is undefined at first check" unless defined? var
 
# Give it a value
var = "Chocolate"
 
# Check to see whether it is defined after we gave it the
# value "Chocolate"
puts "var is undefined at second check" unless defined? var
 
# I don't know any way of undefining a variable in Ruby
 
# Because most of the output is conditional, this serves as
# a clear indicator that the program has run to completion.
puts "Done"