I also showed 2 popular ways of having Perl dump the structure for you. Data::Dumper is a CORE module and will always be available. Data::Dump will usually be available. Note that pp outputs to stderr and so I had to turn the buffering of stdout off in order for the printout to come out in the expected order.

use strict;
use warnings;
use Data::Dump qw(pp);
use Data::Dumper;
$|=1;  #turn off stdio buffering


my %HoH = ( "2023-01-01" => { "00:00" => 1234, 
                              "01:00" => 789,
                              "02:00" => 456, }, 
                              
            "2023-02-01" => { "00:00" => 4321, 
                              "01:00" => 987,
                              "02:00" => 654,  },);

for my $dia (sort keys %HoH){
        print "<br>$dia: \n";
        for my $horarios (sort keys %{$HoH {$dia}}){
                print "$horarios=>" . $HoH{$dia}{$horarios} . "\n";
        }
}

print "VALUE:<br>";
print $HoH{"2023-01-01"}{"00:00"};  #I couldn't see the value

print "\n\n";
pp \%HoH;

print "\n\n";
print Dumper \%HoH;

__END__
Prints:
br>2023-01-01: 
00:00=>1234
01:00=>789
02:00=>456
<br>2023-02-01: 
00:00=>4321
01:00=>987
02:00=>654
VALUE:<br>1234

{
  "2023-01-01" => { "00:00" => 1234, "01:00" => 789, "02:00" => 456 },
  "2023-02-01" => { "00:00" => 4321, "01:00" => 987, "02:00" => 654 },
}


$VAR1 = {
          '2023-02-01' => {
                            '01:00' => 987,
                            '02:00' => 654,
                            '00:00' => 4321
                          },
          '2023-01-01' => {
                            '00:00' => 1234,
                            '02:00' => 456,
                            '01:00' => 789
                          }
        };
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