I think this:

        ($remote_mt,$local_mt) = +(split)[0,1] if (/nfs/i);
        $hash {$remote_mt} = $local_mt;
[download]

...should be this:

         if ( /nfs/i ) {
             ($remote_mnt,$local_mnt) = +(split)[0,1];
             $hash {$remote_mnt} = $local_mnt;
         }
[download]

Also, you've misnamed/typoed your *_mnt variables in several places. If you'd Use strict and warnings, this would jump out.