use strict;
use warnings;
use feature 'say';
use CAM::PDF;

my $pdf  = CAM::PDF-> new( $ARGV[ 0 ]) or die;
my $page = $pdf-> getPage( 1 );
my $anns = $pdf-> getValue( $page-> { Annots } or die );
for ( @$anns ) {
    my $ann = $pdf-> getValue( $_ );
    next unless $pdf-> getValue( $ann-> { Subtype }) eq 'Highlight';
    say $ann;
    say "\t$_" for map $pdf-> getValue( $_ ), 
        @{ $pdf-> getValue( $ann-> { QuadPoints })}
}

__END__

HASH(0xd79f0c)
        237.641
        651.308
        271.059
        651.308
        237.641
        641.602
        271.059
        641.602
        61.4118
        637.963
        92.1406
        637.963
        61.4118
        628.257
        92.1406
        628.257
HASH(0xe8f43c)
        288.529
        611.271
        320.753
        611.271
        288.529
        601.566
        320.753
        601.566