Here is your module implemented as an inside-out class:

package MyMod;

use strict;
use warnings;
use Carp;
use Scalar::Util qw(refaddr);

# Have a private hash for each attribute
my %atr1;    # Attribute 1
my %atr2;    # Attribute 2
             # etc.
             
# This hash is used by the general purpose accessors
my %hashrefs = ( atr1   => \%atr1,
                 atr2   => \%atr2,
                 #etc 
                );
                    

sub new {
  my $class = shift;
  my %args = @_;
  
  # create some unique number from a reference
  my $self = \do{my $dummy};
  my $key = refaddr($self);
  
  $atr1{$key} = $args{'atr1'};
  $atr2{$key} = $args{'atr2'};
  # more attributes...
  
  
  bless($self, $class);
  # ... some code to populate attribs from passed parms
  return $self;
}

# General purpose get/set

sub set {
   my ($self, $attr, $value) = @_;
   my $key = refaddr $self;
      
   if (exists $hashrefs{$attr} ) {
      $hashrefs{$attr}{$key} = $value
   }
   else {
      carp "Invalid attribute name $attr"
   }
}

sub get {
   my ($self, $attr) = @_;
   my $key = refaddr $self;
   
   
   if (exists $hashrefs{$attr} ) {
      return $hashrefs{$attr}{$key}
   }
   else {
      carp "Invalid attribute name $attr";
      return;
   }
}

# MUST have a destructor
sub DESTROY {
    my ($self) = @_;
    my $key = refaddr $self;
      
    delete $atr1{$key};
    delete $atr2{$key};
    # likewise for other attribute hashes
}

1;
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And here is the user code:

use strict;
use warnings;

use MyMod;
my $mm = MyMod->new(atr1 => 1, atr2 => 'string2');

print $mm->get('atr1')."\n";
print $mm->get('atr2')."\n";
$mm->set('atr1', 42);
print $mm->get('atr1')."\n";

$mm->{atr1} = 3000;    <<<<---- Fails "Not a HASH reference"
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