for my $next (@ARGV) {    
   opendir(PWD, "$next") and do {
      my @files = readdir(PWD) or die "$next: $!";
      closedir(PWD);
      print join("\n", @files), "\n";    
   }
}
[download]

TIMTOWDI. I personally find this a little clearer, and is no less idiomatic:

foreach my $next (@ARGV) {    
   if (opendir(PWD, "$next")) {
      my @files = readdir(PWD) or die "$next: $!";
      closedir(PWD);
      print join("\n", @files), "\n";    
   }
}
[download]

While using and and do like that is only slightly less clear than using a true 'if' block, it is slightly less clear than using a true 'if' block. :)