Tip #1 from the Basic debugging checklist: warnings 

readdir() attempted on invalid dirhandle DIR at 
closedir() attempted on invalid dirhandle DIR at

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Using lexical filehandles seems to work for me: 

use warnings;
use strict;
use Cwd;

## cwd  
my $cwd = getcwd; 

## Get files from cwd 
my $res = _list_files($cwd);

sub _list_files {

        my $dir = shift;
        my $files = shift;

        opendir(my $dh, $dir) || die "Error opening: $dir\n";

        while (my $fn = readdir($dh)) {

                ## skip hidden
                next if $fn =~ /^\./;

                ## file, fullpath name
                my $file = $dir . "/" . $fn;

                ## add
                push(@{ $files }, $file); 

                ## dir, decend
                if (-d $file) {

                        ## sub-directory files
                        $files = _list_files($file, $files);
                }
        }

        closedir($dh);

        return $files;
}

[download]

See also:

In reply to Re: Descending a directory tree, returning a list of files by toolic
in thread Descending a directory tree, returning a list of files by Rodster001

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