#!usr/bin/perl
$k = 1;
$file_name = "QoEWeb_DB_Log.txt"; #An input LOG file which holds infor
+mation about different users. 
open(SW,$file_name) or die "ERROR OPENING IN FILE";

open FILE, ">output.txt" or die "ERROR..unable to write" ; #Will write
+ the result into an OUTPUT file. 
while (<SW>)
{
chomp($eachline);

    @file_name1 = ("Carlo_Arnold_2.232_Final.txt", "Sohaib_Ahmad_2.225
+_Final.txt"); #Input LOG files; Each file holds informaton about Indi
+vidual user. I will be adding about 30 files here. 
    
    
    @logarray = split(/:/,$_); # Taking required fields from the first
+ input file.
    $field1 = @logarray[2]; 
    $field2 = @logarray[4];    
    $key1 = @logarray[8];
    $field5 = @logarray[6];
    
    $x = scalar(@file_name1);
    for($j=0;$j<$x;$j++)
    {
     open(RW,@file_name1[$j]) or die "ERROR OPENING IN FILE";
     while (<RW>)
     {
     chomp($eachline);
         @ff_array = split(/:/,$_); #Taking required fields from the s
+econd set of input files. 
         $key2 =  @ff_array[0];
         $field3 = @ff_array[1];
         if( $key1 == $key2) # Finding a match between the two input f
+iles 
            {
               
               print  FILE "$field1:$field2:$key1:$field5:$field3"; #P
+rinting the desired result from both batch of input files. 
               
            }
      
             
        }
        



}
    


}
close FILE;    
close SW or die "Cannot close";
close RW or die "Cannot close";
[download]

Instead of while (<RW>) you can write for (sort <RW>) and be done.

But I strongly recommend to use strict; use warnings; and to declare your variables with my.

Changing the code as you advised; but still the same result: not effect on sorting. Am i missing something here


#!usr/bin/perl

use strict; 
use warnings; 

my $file_name;
my $field1;
my $field2;
my $key1;
my $key2;
my $field5;
my $field3;
my $k;
my $j;
my $x;
my $eachline = 0;
my $eachline1 = 0;

my @logarray;
my @ff_array;
my @file_name1;



$k = 1;
$file_name = "QoEWeb_DB_Log.txt"; #An input LOG file which holds infor
+mation about different users. 
open(SW,$file_name) or die "ERROR OPENING IN FILE";

open FILE, ">output.txt" or die "ERROR..unable to write" ; #Will write
+ the result into an OUTPUT file. 
for (sort <SW>) 
{
chomp($eachline);

    @file_name1 = ("Carlo_Arnold_2.232_Final.txt", "Sohaib_Ahmad_2.225
+_Final.txt"); #Input LOG files; Each file holds informaton about Indi
+vidual user. I will be adding about 30 files here. 
    
    
    @logarray = split(/:/,$_); # Taking required fields from the first
+ input file.
    $field1 = $logarray[2]; 
    $field2 = $logarray[4];    
    $key1 = $logarray[8];
    $field5 = $logarray[6];
    
    $x = scalar(@file_name1);
    for($j=0;$j<$x;$j++)
    {
     open(RW,$file_name1[$j]) or die "ERROR OPENING IN FILE";
     for (sort <RW>) 
     {
     
     chomp($eachline1);
         @ff_array = split(/:/,$_); #Taking required fields from the s
+econd set of input files. 
         $key2 =  $ff_array[0];
         $field3 = $ff_array[1];
         if( $key1 == $key2) # Finding a match between the two input f
+iles 
            {
               
               print  FILE "$field1:$field2:$key1:$field5:$field3"; #P
+rinting the desired result from both batch of input files. 
               
            }
      
             
        }
        



}
    


}
close FILE;    
close SW or die "Cannot close";
close RW or die "Cannot close";
[download]