use strict;
use warnings;
use feature qw (say);
use List::Util qw(max);
use Time::Piece;

my @dates = qw{
  12112014
  01052015
  02202015
  03102015
  01012011
  04092015
  09092015
};


say localtime( max map { Time::Piece->strptime( $_, "%m%d%Y" )->epoch } @dates )
  ->strftime("%m%d%Y");

__END__

\Desktop\monks>other_idea.pl
09092015