use File::Basename qw( basename );

sub visit {
   my ($dir, $level) = @_;

   $level ||= 0;
   my $group_indent = ' ' x (2*$level);

   ++$level;
   my $child_indent = ' ' x (2*$level);

   printf($group_indent."Group: %s {\n", $level ? basename($dir) : $di
+r);

   my @file_names = do {
      opendir(my $dh, $dir);
      grep !/^\.\.?\z/, readdir($dh)
   };

   for my $fn (@file_names) {
      my $qfn = "$dir/$fn";
      if (-d $qfn) {
         visit($qfn, $level);
      } else {
         print($child_indent."File: $fn ($qfn)\n");
      }
   }

   print($group_indent."}\n");
}

visit('/proj/newdata');
[download]

Possible improvements:

• Error checking for opendir.
• Error checking for -d (although it's not likely to return an error if you were just able to read the directory).
• Make "$dir/$fn" portable. (It will fail if you give "C:" as the initial directory on a Windows machine if the current directory for drive C: isn't the root directory.)

Update: Was missing top level Group. Fixed.