Net::FTP::Common seems a good bet.

You can get the full dir-listing and if you check the 'perm' key in the hash of each entry, you will see that the first character is either a 'd' for a directory or a '-' for a file.

use Data::Dumper;
use Net::FTP::Common;

           $common_cfg = { Host => 'your.ftp.server', 
                           User => 'anonymous',
                           Pass => 'me@here.there',
                           RemoteDir  => '/'
                           } ;   

           $ftp = Net::FTP::Common->new($common_cfg, Debug => 0);
           @dir = $ftp->dir();
           print Dumper(\@dir);
           $ftp->quit;
[download]

Warning: Tested on a Windows XP Home Edition system. YMMV on Unix