Dynamically select column based on information from another column

[stephouyang]

Hi, 

I'm trying to select all the columns that end in the value of the last column. How can I do that? 

My last column is dynamic, for period 1 it will show _1, period 2 it will show _2, etc.

When it's period _1 (which is the last column in the input file), I want to select 2 columns "PERIOD_1" & "C_PERIOD_1".

When it's period _2 , I want to select 2 columns "PERIOD_2" & "C_PERIOD_2".

Attached a sample input file.

Many thanks! 

[stephouyang]

Thank you all for the reply! The solutions are so simple yet brilliant.