#!/usr/bin/perl 

# http://www.perlmonks.org/?node=1087227

use strict;
use warnings;

my $months = {
    "Jan" => "01", "Feb" => "02", "Mar" => "03", "Apr" => "04", "May" => "05", "Jun" => "06",
    "Jul" => "07", "Aug" => "08", "Sep" => "09", "Oct" => "10", "Nov" => "11", "Dec" => "12",
};

my $data = {
    "Jul11" => 2, "Dec13" => 2, "Jan14" => 2, "Aug13" => 2,
    "Jun11" => 2, "Apr13" => 2, "Mar12" => 2, "May14" => 2,
};

# using regular sort
print "before:\n";
foreach my $key (sort keys %$data) {
    print "Key - $key  and b value - $data->{$key}\n";
}

# using sortKeys sort
print "after\n";
foreach my $key ( sort { sortKeys( $a, $b ) } keys %$data ) {
    print "Key - $key  and b value - $data->{$key}\n";
}

sub sortKeys {
    ( my $left  = $a ) =~ s/(\D+)(\d+)/$2 . $months->{$1}/e;
    ( my $right = $b ) =~ s/(\D+)(\d+)/$2 . $months->{$1}/e;
    return ( $left cmp $right );
}

__output__
$ ./node_id_1087227_hashkey_sort.pl 
before:
Key - Apr13  and b value - 2
Key - Aug13  and b value - 2
Key - Dec13  and b value - 2
Key - Jan14  and b value - 2
Key - Jul11  and b value - 2
Key - Jun11  and b value - 2
Key - Mar12  and b value - 2
Key - May14  and b value - 2
after
Key - Jun11  and b value - 2
Key - Jul11  and b value - 2
Key - Mar12  and b value - 2
Key - Apr13  and b value - 2
Key - Aug13  and b value - 2
Key - Dec13  and b value - 2
Key - Jan14  and b value - 2
Key - May14  and b value - 2