t.pl

use v5.14;

use List::Util qw/sum/;

sub add_to_hash {
    my ( $hash_ref, $key, $value ) = @_;

    $hash_ref->{$key} = $value;
}


sub diff_sum {
    my ( $x_ref, $y_ref ) = @_;

    my $sum_x = sum ( @$x_ref );
    my $sum_y = sum ( @$y_ref );

    return $sum_x - $sum_y;
}

my @a = (1, 2, 5);
my @b = (5, 5);

my $ds = diff_sum( \@a, \@b );