#!/usr/bin/perl -w
use strict;

my @strings = (
   "PROCESS_DT IN '01/01/2009'", 
   "PROCESS_DT IN '05/23/2006'", 
   "PROCESS_DT IN '01/01/2011'", 
   "PROCESS_DT IN '04/19/2009'", 
   "PROCESS_DT IN '07/01/2009'", );
   
   
@strings = sort { 
                   my ($monthA, $dayA, $yearA) = $a =~ m|(\d+)/(\d+)/(\d+)|;
                   my ($monthB, $dayB, $yearB) = $b =~ m|(\d+)/(\d+)/(\d+)|;
                          "$yearA$monthA$dayA" cmp "$yearB$monthB$dayB"
                }@strings;

print join("\n",@strings),"\n";

__END__
PROCESS_DT IN '05/23/2006'
PROCESS_DT IN '01/01/2009'
PROCESS_DT IN '04/19/2009'
PROCESS_DT IN '07/01/2009'
PROCESS_DT IN '01/01/2011'