Hashes are very useful for matching.

use strict;
use warnings;

my %lookup;

{
   open(my $file1, '<', 'file1.txt') or die("...");

   while (<$file1>) {
      chomp;
      my @fields = split(/\|/, $_);
      $lookup{$fields[0]}{$fields[1]} = $fields[2];
   }
}

{
   open(my $file2, '<', 'file2.txt') or die("...");

   while (<$file2>) {
      chomp;
      my @fields = split(/\|/, $_);

      if (exists $lookup{$fields[0]}{$fields[1]}) {
         $fields[3] = $lookup{$fields[0]}{$fields[1]};
      } else {
         $fields[3] = 'NO MATCH';
      }

      print(join('|', @fields), $/);
   }
}

[download]

Tested.

In reply to Re: Substitute text string in a file with matching text from another file by ikegami
in thread Substitute text string in a file with matching text from another file by tariqahsan

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