readline() on unopened filehandle at ...

##</code><code>##

readline() on unopened filehandle at ... (#1)
    (W unopened) An I/O operation was attempted on a filehandle that was
    never initialized.  You need to do an open(), a sysopen(), or a socket()
    call, or call a constructor from the FileHandle package.

##</code><code>##

use warnings;
use strict;

my $path = '/var/log/*';
my @files = grep { -f } glob $path;