#!/usr/bin/perl

use strict;
use warnings;
use File::Find;

print "Content-type: text/html\n\n";

my $startdir = '/path/to/startdirectory';
my @dirs;

find(\&find_dirs,$startdir);
print_select(\@dirs);

sub find_dirs{
     push(@dirs,$File::Find::name) if(-d $File::Find::name);
}# find_dirs

sub print_select{
     my ($dir_ref) = @_;
     print "<select><option>".join('</option><option>', @$dir_ref).'</option></select>';
}