in reply to Processing files column-wise

This still sounds like line-by-line processing. If not, maybe you can give some example data, input and output. But I'm picturing this: 

open files for writing: file1, file2, file3, file4
for each input file
  get first input line
  look at the headers and set up a map of which fields go where
  while get an input line
    split it into fields
    print the fields to the appropriate output files based on the map

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Aaron B.
My Woefully Neglected Blog, where I occasionally mention Perl.

In Section Seekers of Perl Wisdom