my $newest = shift @{[sort {-M $a > -M $b} (<img*.jpg>)]};

use FindBin;
my $dir = $FindBin::Bin;# aktuelles verzeichnis
opendir(DIR, $dir) or die $!;

my ($lastM, $fileNewest);
while (my $file = readdir(DIR)) {
  next unless $file =~ /\.[Jj][Pp][Gg]$/;
  next unless -f "$dir/$file";
  if (-M _ > $lastM) {
    $lastM = -M _;
    $fileNewest = "$dir/$file";
  }
} # while
if (defined $lastM) {
  print "Datei: $fileNewest\n";
} # if
closedir(DIR);