I think he means situations where he is denied read access to a directory:
$ echo $EUID
1000
$ ls -ld /var/log/apache2
drwxr-x--- 2 root adm 12288 Mar 18 06:25 /var/log/apache2
$ ls -l /var/log/apache2
ls: cannot open directory /var/log/apache2: Permission denied
$ perl -E 'say ((-e q-/var/log/apache2/access.log-) ? "exists" : "not
+exists: $!")'
not exists: Permission denied
# echo $EUID
0
# perl -E 'say ((-e q-/var/log/apache2/access.log-) ? "exists" : "not
+exists: $!")'
exists
He probably just should examine $!