If you edit your post and put <code> tags around your data, as you did with your code in your first post in this thread, we'll be able to read it.

Okay, it sounds like you have a fairly typical "match lines from fileA to lines in fileB" problem, with the added feature of needing to match three fields instead of just one. So the standard solution is to go through one file (usually the smaller one to keep memory use lower), creating a hash of keys with the important fields from that file, then go through the other file line-by-line, checking each line to see if its fields are found in the hash. In pseudo-code:

create a %hash
open fileA
while get a line from fileA
  parse out the three important fields from the line
  concat those fields into a single string
  put that string in the hash as a key, with the line as its value
close fileA
open fileB
while get a line from fileB
  parse out the three important fields from this line
  concat those fields into a single string
  if that string exists as a key in the hash
     print out this line and the value of the matching hash key
close fileB
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One caveat: this only works if the keys created from fileA are unique. If it's possible for multiple lines to have the same key (the same first three column values), you'll have to get a bit more complicated.

Hi Thanks.Below is the code i tried but it does not print anything to the STDOUT.

    #!usr/bin/perl
      use strict;
      use warnings;

      my ($infile1,$infile2) = @ARGV;
      open (IFILE1, "<", $infile1) || die "Cannot open        $infile1
+:$!\n";
      open (IFILE2, "<", $infile2) || die "Cannot open $infile2:$!\n";

     my @array1;
     my %hash1;
     my $str;
     while (<IFILE1>) {
         @array1 = split (" ", $_);
         $str = $array1[0]."\t".$array1[1]."\t".$array1[2];
     $hash1{$str} = 1;
    }
    close IFILE1;
     my @array2;
     my $string;
    while (<IFILE2>) {
        @array2 = split (" ", $_);
        $string =  $array2[0]."\t".$array2[3]."\t".$array2[4];
        #print "$string\n";
        if (exists($hash1{$string})) {
          print "$string\n";
        }
    }
    close IFILE2;
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Hey thanks.The code i sent works with the other pair of input files. I guess there is no line common between file1.txt and file2.txt that is why it does not print anything.