sub add {
   open FH, "<$file" or die $!;
   &lock( *FH );
   $/ = "\;\n\n";
   my @array = <FH>;
   &unlock( *FH );
   close FH;
   push @array, $my_long_domain_string_you_have;
   @array = sort @array;
   my $tempfile = "$file." . time();  # Unique id
   open FH, ">$tempfile" or die $!;
   &lock ( *FH );
   print FH @array;
   &unlock( *FH );
   close FH;
   # rename $file, "$file.old" or die $!;  
       #Backup if desired
   rename $tempfile, $file or die $!;
}