A quick demo of the difference between puts & return for calling methods

puts_vs_return.rb

def addstring(x,y)
  z = x + y 
  return z
end

def putstring(x,y)
  z = x + y 
  puts z
end

##########
# OUTPUT #
##########

>>   words = addstring(addstring("Have ","Fun "),"Today") 
=> "Have Fun Today"

>>   words = putstring(addstring("Have ","Fun "),"Today")  # notice putting a return call on a method still works                      
Have Fun Today
=> nil

>>  words = putstring(putstring("Have ","Fun "),"Today")                            
Have Fun 
NoMethodError: undefined method `+' for nil:NilClass
        from /home/james/lab/scratch/puts_vs_return.rb:7:in `putstring'
        from (irb):11
        from /home/james/.rbenv/versions/2.2.0/bin/irb:11:in `<main>'
>>