.... $VAR1->[0], $VAR1->[0], $VAR1->[0], ...

This means you are looking at copies of the same reference.

Win8 Strawberry 5.8.9.5 (32)  Thu 05/12/2022 17:00:05
C:\@Work\Perl\monks
>perl

use strict;
use warnings;

use Data::Dumper;

my $array_ref = [ ([ qw(a b c) ]) x 4 ];

print "@$array_ref \n";
print Dumper $array_ref;

^Z
ARRAY(0x983824) ARRAY(0x983824) ARRAY(0x983824) ARRAY(0x983824)
$VAR1 = [
          [
            'a',
            'b',
            'c'
          ],
          $VAR1->[0],
          $VAR1->[0],
          $VAR1->[0]
        ];
[download]

I already solved my problem, posted about it. But wanted to further explain what you pointed out.

I don't believe that I am looking at copies of the same reference

sub makeJSONToExport {
    my ($arrayref) = @_;

    my $typehint_raw =  {    age        => JSON_TYPE_INT,
              lastname      => JSON_TYPE_STRING,
              firstname          => JSON_TYPE_STRING};

    my $typehint_raws = [ ($typehint_raw) x  @$arrayref];
    my $json = encode_json($arrayref, $typehint_raws);
    return $json;
}
[download]

I'm looking at $typehint_raws just before calling the encode_json command. So I believe I am seeing it just after it's initialized for the proper size, but before it's filled in by encode_json

    ...
    my $typehint_raws = [ ($typehint_raw) x  @$arrayref];
    my $json = encode_json($arrayref, $typehint_raws);
    return $json;
    ...
[download]

I'm looking at $typehint_raws just before calling the encode_json command.

If you're dumping $typehint_raws just before calling encode_json(), then you're dumping it just after initializing it (according to the posted code). In that case, the situation is just as given in the example here except that it's a hash reference that's being replicated rather than an array ref.

I don't know what encode_json() does to "fill in" $typehint_raws, but it doesn't seem that it can be of much consequence since $typehint_raws goes out of scope with the return statement that immediately follows the subroutine call.

---

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