$ perl -Mstrict -Mwarnings -E '
my @dates = qw{
   12112014
   01052015
   02202015
   03102015
   01012011
   04092015
   09092015
   };

say for
   map { substr $_, 8 }
   sort                          
   map { join q{}, ( unpack q{a2a2a4}, $_ )[ 2, 0, 1 ], $_ }
   @dates;'
01012011
12112014
01052015
02202015
03102015
04092015
09092015
$