I think you will find it convenient to use Tie::File to edit your file in-place. Something like 
use strict;
use warnings;
use Tie::File;

tie my @lines, 'Tie::File', filename or die ...;
for (@lines) {
  s/(?=(\d+)$)/ 'Warning! ' if $1 < 4_000_000_000/e;
}

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Caution: Contents may have been coded under pressure.

In reply to Re: compare size by Roy Johnson
in thread compare size by Anonymous Monk

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