use strict;
use warnings;
use Data::Dumper;
#use Data::Dumper::Concise; # i prefer Data::Dumper::Concise
use XML::Twig;

# individually process each <signal> element
sub signal_handler {
        my ($data, $twig, $elem) = @_;

        # get the attributes of $elem (<signal>)
        my $atts = $elem->atts();  

        if ($atts->{'sigid'} == 3464) {
                print "Found <signal> with sigid == 3464:\n",$elem->sprint(),"\n";
                print "<PRESS ENTER TO CONTINUE>";<STDIN>;
        }

        # if you want to access the element in a way similar to XML::Simple:
        my $xml_simple_style_elem = $elem->simplify();

        # check out the simplified structure:
        print Dumper($xml_simple_style_elem);
        print "<PRESS ENTER TO CONTINUE>";<STDIN>;

        # Example for Data Collection:
        my ($sigid, $id) = @{$atts}{qw/sigid id/};
        if (defined $sigid and defined $id) {
                $data->{sigid_id_count}{$sigid}{$id}++;
        }

        # get all elements below <signal> which are called <foo>
        my @foo_subelements  = $elem->descendants('foo');

        $twig->purge; # explicitly free the memory
};

sub main {
        my $fn = shift @ARGV;
        my %collected_data;

        my $twig = XML::Twig->new(
                twig_roots => {
                        'signal'     =>  sub {signal_handler(\%collected_data, @_);},
                },
        );
        eval {
                $twig->parsefile($fn);
        };
        if ($@) {
                print STDERR "Failed to parse '$fn' ($@)\n";
        }
        if (%collected_data) {
                print "I collected the following data:\n",Dumper(\%collected_data);
        }
}
main();