Your problem may be that your $_ does NOT contain full path to the item in question.

Change your code to die() if not a dir and tell you what it tested for.

use Cwd;

foreach(@dir) {
   if (-d$_) { print $_," is a directory.\n"; }
   else { die("Not a dir '$_', current working directory is: ". cwd())
+; }
}
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