#!perl -l

# TESTED WITH v5.6.1 (MSWin32-x86-multi-thread) ONLY!

require 5.006;

use strict;
use File::Find 'find';

my $INDENT_DELIM = '  ';
my $DEPTH        =    0;

find(
  {
    wanted      => \&wanted,
    preprocess  => \&pre,
    postprocess => \&post,
  },
  @ARGV ? @ARGV : "."
);

sub pre {
    print indent( '<li id="folder">' . $_ . '</li>' );
    print indent( '<ul>'                            );

    $DEPTH++;

    @_;
}

sub post {
    $DEPTH--;

    print indent( '</ul>'                           );
}

sub wanted {
    return if -d;
    print indent( '<li>' . $_ . '</li>'             );
}

sub indent {
    return $INDENT_DELIM x $DEPTH . $_[0];   
}