the second "our @sums" inside the END block is not needed

Good point! I have often needed a second 'our' in a BEGIN block at the start of a file when using "-n". I never noticed that an END block at the end is included in the scope of the first 'our'. Note that if we change the single 'our' to 'my', the code still compiles without error. It fails to execute correctly due to life-time issues, not scope.