my @items   = qw/a  b  c  d  e/;
my @weights = (0.1, 2, 1, 4, 1.3);
my @summed_weights;

my $running_sum = 0;
for (@weights) {
    $running_sum += $_;
    push @summed_weights, $running_sum;
}
use Data::Dumper;
print Dumper \@summed_weights;