Sort Date in "DD MMM YYYY" format

To sort date in "DD MMM YYYY" format (e.g. "02 DEC 2010")

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

# Constants
my %MONTH_NUMBER = (
    'JAN' => 1,
    'FEB' => 2,
    'MAR' => 3,
    'APR' => 4,
    'MAY' => 5,
    'JUN' => 6,
    'JUL' => 7,
    'AUG' => 8,
    'SEP' => 9,
    'OCT' => 10,
    'NOV' => 11,
    'DEC' => 12,    
);

my @myarray = (
    '08-DEC-10',
    '30-NOV-10',
    '26-NOV-10',
    '25-NOV-10',
    '25-NOV-10',
    '24-NOV-10',
    '11-NOV-10',
    '10-NOV-10',
    '10-NOV-10',
    '08-NOV-10',
    '03-NOV-10',
    '02-NOV-10',    
    '01-NOV-10',
);

my @sorted_array = sort sort_func @myarray;

print "@sorted_array"; 

####################
# Subroutine
####################
# Sort function
sub sort_func() {
    # To sort in desc, just swap $a and $b
    #return convert_datenumber($b) 
    #   cmp convert_datenumber($a);
  
    return convert_datenumber($a) 
       cmp convert_datenumber($b);
}

# Convert "DD MMM YYYY" into "YYYYMMDD"
sub convert_datenumber() {
    my $in_date = $_[0];
    
    my $out_date = 0;
            
    if (length($in_date)) {
        my $day        = substr($in_date, 0, 2);
        my $month      = $MONTH_NUMBER{ substr($in_date, 3, 3) };
        my $year       = substr($in_date, 7);
        
        $out_date = $year * 10000 
                  + $month * 100
                  + $day;                                    
    }
        
    return $out_date;
}

Output:

01-NOV-10 02-NOV-10 03-NOV-10 08-NOV-10 10-NOV-10 10-NOV-10 11-NOV-10 24-NOV-10 25-NOV-10 25-NOV-10 26-NOV-10 30-NOV-10 08-DEC-10