Using `+=` will create a local copy of variable instead of updating the reference

errors.rb

# Example 1
errors = []
def add_error_1(errors, arr)
  errors += arr # this won't change the errors outside, instead of copy of errors will be created locally
  puts "inside of func: #{errors.inspect}"
end

add_error_1(errors, ['an error 1']) # inside of func: ["an error 1"]
puts "outside: #{errors.inspect}" # outside: []


# Example 2
errors = []
def add_error_2(errors, arr)
  arr.each do |e|
    errors << e # this changes errors outside
  end
  puts "inside of func: #{errors.inspect}"
end

add_error_2(errors, ['an error 2']) # inside of func: ["an error 2"]
puts "outside: #{errors.inspect}" # outside: ["an error 2"]