Elements in File1:
1. Hi
2. March
3. Aug
4. Sept
5. Oct

Elements in File2:
1. March
2. Hi
3. Bye
4. Aug
5. Dec

Elements in File3:
1. Hi
2. March
3. Aug
4. Sept
5. Oct

Elements in File4:
1. Hi
2. March
3. Aug
4. Bye
5. Dec



##</code><code>##

my hoh;
my hash;

for(my $i = 0; $i <= 3; $i++){

my $condition = "first" if ($i == 0);
$condition = "second" if ($i == 1);
$condition = "third" if ($i == 2);
$condition = "forth" if ($i == 3);

## Reading the file
open my $IN, $i.".txt or die $!;
while(<$IN>){
chomp($_);
my $ele = $_;
$hoh{$i}{$_} = 1;
### Look for that element if it exists in $hoh{$i}{$_} if $i >=1 for all $i

## for the first file
if (!exists $hash{$_}){
$hash{$_} = 10**$i;
}
elsif ($i >= 1){
#### code to check the common element in all $i
#### if the common element is present then
my val = $hash{$_}
my newVal = int($val) + 10**$i; 
$hash{$_} = newVal;
}
}
close($IN);
}