my $oldest;
my $oldtime = 0;
for (glob "$dir/*.pl") {
  my $thistime = -C;
  if ($thistime > $oldtime) {
    ($oldest, $oldtime) = ($_, $thistime);
  } 
}

##</code><code>##

use List::Util 'reduce';
my $file = (reduce {$a->[0] < $b->[0] ? $a : $b}
                   map {[(stat)[10],$_]}
                   glob '*.pl'
           )->[1];

##</code><code>##

my $file = reduce {(stat $a)[10] < (stat $b)[10] ? $a : $b}
                  glob '*.pl';