Then build the ruleset in the script, something like:

use XML::Rules;

@ARGV == 5 or die "Usage: BookStore3.pl roottag datatag idtag fitertag
+ filtervalue\n";

my ( $roottag, $datatag, $idtag, $fitertag, $filtervalue) = @ARGV;


my $parser = XML::Rules->new(
    rules => [
        _default => 'content',
        $datatag => sub {
            return unless $_[1]->{$fitertag} eq $_[4]->{parameters};
            my $id = delete $_[1]->{$idtag};
            delete $_[1]->{'_content'};
            return $id => $_[1]
        },
        $roottag => 'pass no content',
    ]
);


my $data = $parser->parse(\*DATA, $filtervalue);

use Data::Dumper;
print Dumper( $data);

__DATA__
<?xml version="1.0" encoding="ISO-8859-1"?>
<bookstore>
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and called as

BookStore3.pl bookstore book title category CHILDREN
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