#!/usr/bin/perl;
use warnings;
use strict;

# I am not sure what data set you have?
# yyyy-mm-dd will sort in ASCII order
# with a simple sort.

# yyyy-dd-mm or mm-dd-yyyy is a bit more
# complex, eg: 2013-11-07 vs 11-07-2013.

# It is possible to detect yyyy-mm-dd
# versus yyyy-dd-mm or mm-dd-yyyy, however
# dd vs mm can be quite problematic.
# 02-03-2011 vs 03-02-2011?

# the code that you show is actually rather
# strange looking.

what are your trying to do?
show some input and expected output.