Select Code to Download

for each item in items:
    for each keyword in item.keywords:
...
for each item in items:
    sort keywords by frequency
    push hierarchy{sorted keywords}, item

  item = 1, keywords = a b c
  item = 2, keywords = b c
  item = 3, keywords = d b

a = 1, b = 3, c = 2, d = 1

b/c/2
b/c/a/1
b/d/3

my @items;

...
}

print "$_\n" for sort @nodes