Is that large amount of code necessary to ask how to iterate over an array that you only have a reference to?

Please read perlreftut and/or References Quick Reference. They explain about references and how to iterate over array references. Also see Data::Dumper for printing out the data structure you have.

Most likely you just want:

use Data::Dumper;
for my $key (keys %{ $dec_json_obj->{item_json_array}->{REQUEST}->{Ite
+ms} }) {
    print "Key: $key\n";
    print "Value: " . Dumper $dec_json_obj->{item_json_array}->{REQUES
+T}->{Items}->{ $key };
};
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