Change values in a hash without modifying the origional?

example.rb

arr = [{num: 1}, {num: 2}, {num: 3}]
arr.map{|h| h[:num] += 1; h} # [{:num=>2}, {:num=>3}, {:num=>4}]
arr # [{:num=>2}, {:num=>3}, {:num=>4}]

# is there a better way to do this?
arr = [{num: 1}, {num: 2}, {num: 3}]
arr.map{|h| clone = h.clone; clone[:num] += 1; clone} # [{:num=>2}, {:num=>3}, {:num=>4}]
arr # [{num: 1}, {num: 2}, {num: 3}]