use warnings;
use strict;
use JSON;

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

my $data = decode_json($original);

for my $key ( keys %{ $data } )
{
    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};
        print "  -> Putting it back under sub-structure with key 'scheduled'\n";
        $data->{scheduled}{$key} = $value;
    }
    else
    {
        print "  -> It's fine where it is, no action taken\n";
    }
}

print encode_json( $data ), $/;