Thank you for your time and effort with your reply

I really appreciate it.

Below is just your code with some comments/questions etc.

Would appreciate your comments at some stage.

I am really still learning Perl.

use warnings;
use strict;
use JSON;
use Data::Dumper;

my $original = '{"OWNER":"KeyProjects","age1":null,"ht1":null}';
[download]

#Literal entry.

my $desired  = '{"OWNER":"KeyProjects","scheduled":{"age1":null,"ht1":null}}';

#Literal entry.

my $data = decode_json($original);
print Dumper $original;
print Dumper $desired;
print Dumper $data;
for my $key ( keys % {$data}  )
[download]

#Converts $data into a hash and cycles through it.

{
    print "Found a key: $key", $/;
    if ( $key =~ /\A (?: age\d+ | ht\d+ ) \z/x )
    {
        print "  -> It matches our regular expression\n";
        print "  -> Deleting it from data structure\n";
        my $value = delete $data->{$key};
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#Does this delete the pair, the value, or what? See below.

        print Dumper $key;
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#Looks like nothing is deleted.

        print Dumper $value;
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#Looks like nothing is deleted.

        print "  -> Putting it back under sub-structure with key 'sche
+duled'\n";
        $data->{scheduled}{$key} = $value;
[download]

#I should understand this step but I don't really know what each aspect of this line is doing.

        print Dumper $key;
        print Dumper $value;
        print Dumper $data;
    }
    else
    {
        print "  -> It's fine where it is, no action taken\n";
        print Dumper $key;
        print Dumper $data;
    }
}

print encode_json( $data ), $/;


use Test::More;
my $desired_data = decode_json( $desired );
is_deeply( $desired_data, $data, "Data structures match" );
done_testing(1);
[download]

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