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), $/);
   }
}

##</code><code>##

789|efg|2222222|NO MATCH
123|abc|9999999|777
786|uvw|1234567|NO MATCH
123|xxx|0000000|NO MATCH
234|cde|0000000|456
567|xyz|1111111|999