Your datastructure is not an ideal fit. Instead, try a Hash of Arrays of Hashes:

use strict;
use warnings;
use Data::Dumper;

my %hash;

push @{$hash{alice}}, {aaaa => "20:00:00"};
push @{$hash{john}},  {ccc => "21:00:00"};
push @{$hash{alice}}, {www => "22:00:00"};
push @{$hash{john}},  {aaa => "23:00:00"};
push @{$hash{andy}},  {xxx => "24:00:00"};
push @{$hash{alice}}, {bbb => "25:00:00"};
push @{$hash{andy}},  {yyy => "26:00:00"};

print Dumper $hash{alice};

__END__
$VAR1 = [
          {
            'aaaa' => '20:00:00'
          },
          {
            'www' => '22:00:00'
          },
          {
            'bbb' => '25:00:00'
          }
        ];
[download]

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)