I am having trouble trying to pass a hash as an argument to a module. Ultimately I want to use the hash as an index of column names, but for this post I'll just use toy code. I haven't written a module before and have been following this webpage for guidance:

https://www.perl.com/article/25/2013/5/20/Old-School-Object-Oriented-Perl/

My module code is: 
  1 package toy_module;
  2 
  3 sub new {
  4         my ($class, $args) = @_;
  5         my $self = {
  6                 simple_hash => $args->{simple_hash},
  7                 simple_test_scalar => $args->{simple_test_scalar},
  8         };
  9         print "********** INSIDE SUBROUTINE NEW **********\n";
 10         print "simple scalar: ".$self->{simple_test_scalar}."\n";
 11         print "$_\n" for keys %$self->{simple_hash};
 12         return bless $self, $class;
 13 }
 14 
 15 sub show_simple_hash {
 16         my $self = shift;
 17         print "********** INSIDE SUBROUTINE SHOW_SIMPLE_HASH *****
+*****\n";
 18         print "simple scalar: ".$self->{simple_test_scalar}."\n";
 19         print "$_\n" for keys %$self->{simple_hash};
 20 }
 21 
 22 1;

[download]
And my code to call the module is: 
  1 use strict;
  2 use warnings;
  3 use lib '~/working/toys';
  4 use toy_module;
  5 
  6 my %little_test_hash = (
  7         COL_1 => 0,
  8         COL_2 => 1,
  9         COL_3 => 2,
 10         COL_4 => 3,
 11         COL_5 => 4,
 12 );
 13 my $little_test_hash_ref = %little_test_hash;
 14 
 15 my $test_object = toy_module->new({simple_hash=>$little_test_hash_
+ref, simple_test_scalar=>5});
 16 my $next_test = $test_object->show_simple_hash;

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What I hoped to see was the little_test_hash being passed along (and its keys printed) when test_object is instantiated by the subroutine "new", and then to see it preserved as an attribute (and its keys printed) when the subroutine "show_simple_hash" is called. Instead, this is what I get: 
MacBook-Pro:toys mcrepeau$ perl test_toy_module.pl 
Using a hash as a reference is deprecated at toy_module.pm line 11.
Using a hash as a reference is deprecated at toy_module.pm line 19.
********** INSIDE SUBROUTINE NEW **********
simple scalar: 5
Type of argument to keys on reference must be unblessed hashref or arr
+ayref at toy_module.pm line 11.

[download]
Can anyone help me understand what I'm doing wrong?

In reply to Trouble passing a hash to a module by mcrepeau

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