perl cumulative module question

[ben perl]

Is there a perl module to find cumulative in a column? It should subtract
from the previous row and creates new column.

For example, If i have the follow column in my file

2
6
9

It gives me

2
6-2 = 4
9-4 = 2

So the resulting column is

2
4
2

Hope I am using cumulative as the right word to explain this.

I could write my own script but did not want to reinvent the wheel.


Thanks,
-Bandeep