#!/usr/bin/perl
use common::sense;
use File::Find;

my $dir = "/some/dir/some/where";
my %dirs;

finddepth(\&newest, $dir);

sub newest {
    return unless -f;
    my ($d, $n) = ($File::Find::dir, $File::Find::name);
    $dirs{$d} ||= $n and return;
    $dirs{$d} = $n if (stat($n))[9] > (stat($dirs{$d}))[9];
}

print "$_: $dirs{$_}\n" for keys %dirs;