use strict;
use warnings;
use CAM::PDF;
#...some code here...
#for testing purpose:
my $file='path_to_some.pdf';
#

my $oldpdf = CAM::PDF->new($file) or die "$CAM::PDF::errstr\n";
if ($oldpdf->numPages() > 100) {
	printf " (%d pages)\n", $oldpdf->numPages();
	$oldpdf->extractPages(1..100);
	$oldpdf->cleanoutput("_$file");
}