Bernardo Monteiro Rufino wrote:
> Use it:
> irb(main):001:0> array = [[1], [2]]
> => [[1], [2]]
> irb(main):002:0> array.map{|a| a += [3]}

That expands to:

   array.map{|a| a = a + [3] }

The Array#+ method isn't destructive, and a variable assignment in a 
block isn't either.

-- 
Alex