First of all, thanks for your reply...

Im very ashamed to shoq my code, since it has a lot of bugs, I dont use warnings or stricy(anyway it was only for a quick assigment)...

On the first part of the script, I open both files and using foreach I make a comparison with the grep() function...

On the second part I get the unique lines of the text, because it always repeats the same lines like a dozen times...

The problem is that the files, stays the same after all this slow proces...

Hope you can help me...

#!/usr/bin/perl


#FIRST PART
open(FILE, "email.txt");
@lines = <FILE>;
close(FILE);

open(FILE, "messages.txt");
@data = <FILE>;
close(FILE);

open(FILE, "+>messages.txt");


foreach $data(@data){

foreach $line(@lines){
chomp($line);
($user, $domain) = split("\@", $line);

$a = grep { /$user/ } $data;
$b = grep { /$domain/ } $data;

if($a != 0 && $b != 0){
   print $data;
    }else{
       print FILE $data;

         }

          }


}

close(FILE);


#SECOND PART
open(FILE, "messages.txt");
@list = <FILE>;
close(FILE);

%seen = ();

@unique = grep { ! $seen{$_} ++ } @list;

open(FILE, "+>messages.txt");

foreach $unique(@unique){

  print FILE "$unique";
}

close(FILE);
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