#!/usr/bin/perl
use 5.018;
use PDF::API2;
use strict;
use warnings;

my $path = "./pdfs/";
my $out_pdf_file = 'merged.pdf';
my $out_pdf = PDF::API2->new(-file => $out_pdf_file);

opendir (my $DIR, $path) or die "Could not open $path:\n$!\n$^E";
chdir $path;

while ( my $in_pdf_file = readdir $DIR ) {
  next if $in_pdf_file =~ /^\./;
  
  my $in_pdf = PDF::API2->open($in_pdf_file) or die "Error opening PDF file [$in_pdf_file]:\n$!\n$^E";
  
  foreach my $page ( 1 .. $in_pdf->pages() ) {
    $out_pdf->import_page($in_pdf, $page, 0);
  }
  $out_pdf->update();
}

closedir $DIR;