print vs puts behaviour for overloaded Array#to_s

Hi,
I've come across the following feature when using an overloaded to_s
method on an array. A simple example should explain it best :

class Foo
        attr_reader :a, :b
        
        def initialize
                @a=rand(10)
                @b=rand(10)
        end
        
        def to_s
                ": #{a} #{b} :"
        end
        
        def diff
                a-b
        end
end

test=Array.new
def test.to_s
        str=""
        self.each { |i| str+="| #{i.diff.to_s} " }
        str
end

(1..5).each { test <<  Foo.new }

puts test
puts test.to_s

print test,"\n"
print test.to_s,"\n"

This gives the following results:

: 3 2 :
: 3 6 :
: 0 1 :
: 9 4 :
: 7 1 :
| 1 | -3 | -1 | 5 | 6 
| 1 | -3 | -1 | 5 | 6 
| 1 | -3 | -1 | 5 | 6 

So why does puts no pick up the overladed to_s function defined for
test, whereas print does?

Any help would be appreciated.

Steve