How about something like this:

use strict;
use warnings;

use File::Slurp;

my $dir       = 'C:/';
my $dir_file  = 'C:/directories.txt';
my $file_file = 'C:/files.txt';

my @files_and_dirs = read_dir( $dir );

foreach my $file ( @files_and_dirs ){
    if ( -d $dir.'/'.$file ){
        $file .= "\n";
        append_file( $dir_file, $file );
    }
    elsif ( -f $dir.'/'.$file ){
        $file .= "\n";
        append_file( $file_file, $file );
    }
}
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