comparing these parsers performance

Shall we?

use strict;
use warnings;
use feature 'say';
use Time::HiRes 'time';

use PDF::API2;
use CAM::PDF;
use PDF::Data;

sub with_time ($&) {
    my ( $note, $code ) = @_;
    my $t = time;
    my $ret = &$code;
    printf "%-6.3f - %s\n", time - $t, $note;
    return $ret
}

my $fn = 'HigherOrderPerl-trimmed.pdf';

{   say '    PDF::API2';

    my $pdf = with_time '(1) open (and cache pages)', sub { 
        PDF::API2->open( $fn )
    };
    with_time '(2) parse/cache everything', sub {
        $pdf->{ pdf }->read_objnum( $_, 0 )
            for 1 .. $pdf->{ pdf }{' maxobj'} - 2
    }
}
{   say '    CAM::PDF';

    my $pdf = with_time '(1) open', sub { 
        CAM::PDF->new( $fn )
    } ;
    with_time '(2) parse/cache page objects', sub {
        $pdf->getPage( $_ ) for 1 .. $pdf->numPages
    };
    with_time '(3) parse/cache everything else', sub {
        $pdf->cacheObjects
    }
}
{   say '    PDF::Data';

    with_time '(1) open and parse everything', sub {
        PDF::Data->read_pdf( $fn, '-novalidate' => 1 )
    }
}

__END__

    PDF::API2
0.649  - (1) open (and cache pages)
1.067  - (2) parse/cache everything
    CAM::PDF
0.010  - (1) open
0.097  - (2) parse/cache page objects
0.095  - (3) parse/cache everything else
    PDF::Data
7.002  - (1) open and parse everything
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Modules were created for different tasks/purposes; this comparison is not really practical, just for entertainment and additional proof, to self (though I don't need any), that one parser is superior to alternatives and why I'm using one and won't consider others for my usual purposes, which are inspection/analysis and minor pinpoint changes. If/when I need PDF generation (especially from scratch), there's no choice but PDF::API2.

Just to clarify, (a) PDF::API2 caches all pages to its internal stack on open, therefore I did additional step for CAM::PDF. And so, (1) + (2) for the latter is to be compared to (1) of the former. (b) PDF::Data also decompresses/inflates all streams (though we have prohibited validation), which takes ~0.5 seconds. It could be either disabled (patching source) or turned on for other participants, but I don't think it's important. The comparison is illustration of regex use efficiency to parse.