How big are the other files? If you don't mind loading them into memory: 
use 5.006;  # Uses "open" syntax introduced in Perl 5.6.0.
use strict;
use warnings;

my $output_file_name = shift(@ARGV);
my $main_file_name   = shift(@ARGV);
my @other_file_names = @ARGV;

my @data;

foreach (@other_file_names) {
   open(my $fh_in, '<', $_)
      or die("Unable to open input file $_: $!\n");

   while (my $line = <$fh_in>) {
      # Keep the \n on $line.
      chomp(my $chomped_line = $line);
      my @fields = split(/,/, $chomped_line);
      foreach my $idx (0..$#fields) {
         # Saves a reference instead of a copy to save memory.
         push(@{$data[$idx]{$fields[$idx]}}, \$line);
      }
   }
}

{
   open(my $fh_in, '<', $main_file_name)
      or die("Unable to open input file $main_file_name: $!\n");

   open(my $fh_out, '>', $output_file_name)
      or die("Unable to open output file $output_file_name: $!\n");

   while (my $line = <$fh_in>) {
      print $fh_out ($line);
      chomp($line);
      my @fields = split(/,/, $line);
      foreach my $idx (0..$#fields) {
         if ($data[$idx]{$fields[$idx]}) {
            foreach (@{$data[$idx]{$fields[$idx]}}) {
               print $fh_out ($$_);
            }
         }
      }
   }
}

[download]

Untested. You didn't specify what to do And you should probably use Text::CSV_XS instead of splitting yourself.

Update: Fixed compilation errors.

In reply to Re: How to combine multiple files together by ikegami
in thread How to combine multiple files together by xspikx

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