use strict;
use warnings;

my $dir_qfn = "C:\\inetpub\\performancetesting\\output\\new\\mlx\\aar";

opendir(my $dh, $dir_qfn)
   or die("Can't read dir $dir_qfn: $!\n");

while (defined(my $fn = readdir($dh)) ) {
   my $qfn = "$dir_qfn/$fn";
   next if !-f $qfn;

   open(my $fh, '<', $qfn)
      or do { warn("Can't open file $qfn: $!\n");
              next;
            };

   while (<$fh>) {
      chomp;
      printf("%03d: %s\n", $., $_);
   }
}