Hello monks!

Is it possible to use hash reference as a key in another hash reference?

I realize I am looking for functionality that a database could give me easily but I have been using Perl hashrefs for log analysis and would like to continue that way.

In the below, simplified example I am keeping stats of sales at a burger joint. The hash that I would like to use as a key contains the date and time data (we'll call it the "key hash"). In a current, working system I have a function (basically a join) that is used to convert the "key hash" into a string that becomes the key used to store the sales data. Later on I have to use another function to convert that string back into a hash -- this is fine for homogenous data but I would like to use abstraction to allow dynamic "hash keys" and this idea seemed simpler than having the data carry around it's own transform functions.

I believe that am misunderstanding something fundamental about hash references because the code below seems to work. It takes the "hash key" hash reference and inserts the "stats hash" but when I try to reference the "hash key" I only have a "string" which of course throws up errors. I've tried to re-reference the hash but can't seem to find a way to do it properly.

thanks for whatever help you can provide

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

my $key_hash_1 = { 'day' => 1, 'month' => 1, 'year' => 2000, 'hour' =>
+ 4, 'minute' => 44};
my $key_hash_2 = { 'day' => 1, 'month' => 1, 'year' => 2000, 'hour' =>
+ 4, 'minute' => 45};

my $sales_hash = { 
    $key_hash_1  => {'burgers_sold' => 5, 'fries_sold' => 3, 'sodas_so
+ld' => 11},
    $key_hash_2     => {'burgers_sold' => 2, 'fries_sold' => 4, 'sodas
+_sold' => 7}    
};

print Dumper($key_hash_1,$key_hash_2);
print Dumper($sales_hash);

while (my ($key_hash,$sales) = each (%$sales_hash)){
    print "$key_hash => $sales\n";
    
    while (my ($sales_item,$total_sold) = each(%$sales)){
        print "\t$sales_item => $total_sold\n";
    }
    while (my ($time_item,$time_value) = each(%${$key_hash})){
        print "\t$time_item => $time_value\n";
    }
}
[download]

Results:

$VAR1 = {
          'hour' => 4,
          'minute' => 44,
          'month' => 1,
          'day' => 1,
          'year' => 2000
        };
$VAR2 = {
          'hour' => 4,
          'minute' => 45,
          'month' => 1,
          'day' => 1,
          'year' => 2000
        };
$VAR1 = {
          'HASH(0x904d00)' => {
                                'fries_sold' => 4,
                                'sodas_sold' => 7,
                                'burgers_sold' => 2
                              },
          'HASH(0x815d48)' => {
                                'fries_sold' => 3,
                                'sodas_sold' => 11,
                                'burgers_sold' => 5
                              }
        };
HASH(0x904d00) => HASH(0x90c238)
        fries_sold => 4
        sodas_sold => 7
        burgers_sold => 2
Can't use string ("HASH(0x904d00)") as a SCALAR ref while "strict refs
+" in use
[download]

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