I like this code. I have three suggestions:

1. I'd make $firsttime an explicit package variable (refer to it as $main::firsttime) rather than a top-level lexical. After the top-level while loop, you don't refer to it for a long time, and its appearance in checkfile is a bit disorienting.
2. Instead of running words together in symbol names, I'd separate them with underscores (so $firsttime would become $first_time). This is quite subjective, but I find it much easier to read.
3. The massive if...elsif...elsif...else statement in sub ftp is ugly. :-) I'd use a dispatch table instead:

     my %commands = (
       'LS'   => \&lsftp,
       'DIR'  => \&dirftp,
       'GET'  => \&getftp,
       'PUT'  => \&putftp,
       'DEL'  => \&delftp,
       'SIZE' => \&sizeftp,
     );
   
     [...]
   
     my $cmd = $commands{$type};
     if(&$cmd($value1, $value2) == 1) {
       sleep $idletime;
       next;
     }
   [download]

   It would take a little bit of work to make the interfaces for each command sub identical (or at least compatible), but I think the savings are worth it.

--
The hell with paco, vote for Erudil!
:wq