my $error = 0;
my @tmp = sort datesort qw( 2000-4 2000-2 2000-1 2000-12 2001-1 2002-12 1999-12 );
my($year,$month) = split '-', $tmp[0];
for(my $i = 1; $i < @tmp; $i++) {
  if(++$month == 13) {
    $month = 1;
    $year++;
  }
  if($tmp[$i] ne "$year-$month") {
    print "ERROR! gap at '$year-$month', '$tmp[$i]' found!\n";
    $error = 1;
    last;
  }
}
print "Success\n" unless $error;
sub datesort {
  my($a1,$a2) = split '-', $a;
  my($b1,$b2) = split '-', $b;
  $a1 <=> $b1 or $a2 <=> $b2;
}