As part of your complete solution, perhaps the module File::DirList would be helpful, as you can get the newest file in a directory from it:

use strict;
use warnings;
use File::DirList;

my $dir = '.';
my $newestFile = File::DirList::list( $dir, 'M' )->[0]->[13];
print $newestFile;
[download]

Hope this helps!