#!/usr/bin/perl -w

use strict;

open DATA, "./data.txt"; # or wherever the file is

my @data=<DATA>;

my @sorted = sort sort_func @data ;
for(@sorted){print $_};

sub sort_func{

    my ($a_dd,$a_mm,$a_yy)=$a =~ m|(\d*)/(\d*)/(\d*)|;
    my ($b_dd,$b_mm,$b_yy)=$b =~ m|(\d*)/(\d*)/(\d*)|;
    return ( $a_yy<=>$b_yy 
                || 
             $a_mm<=>$b_mm 
                || 
             $a_dd<=>$b_dd);
}