use strict;
use PDF::API2;

my $pdf = PDF::API2->new( -file => "path/to/outfile.pdf" );
my @files = glob ("path/to/somewhere/else/*.pdf");
merge (@files);

# some stuff

sub merge
{
    my 
    (
        $file,
        $root,
    );

    $root = $pdf->outlines;

    my $import_page = 0;
    my $document_page = 0;

    foreach $file ( @_ )
    {
        my ($inputpdf, $inputdir) = fileparse ($file);       

        my $input = PDF::API2->open( $file );

        my @pages = 1 .. $input->pages;

        if ( scalar @pages > 0 ) 
        {
            my $outline;

            $outline = $root->outline
                if $bookmark;

            foreach ( @pages ) 
            {
                ++$import_page;
                ++$document_page;

                my $page = $pdf->importpage($input, $_, $import_page);

                if ( $bookmark )
                {
                    my ($bmtext) = ($inputpdf =~ /([^\.]+)/ );
                    $outline->title($bmtext);

                    my $bm = $outline->outline;
                    $bm->title("Seite $document_page");

                    $bm->dest($page);
                    $outline->dest($page) if $document_page == 1;
                    $outline->closed;
                }
            }

        }
    }
    
    $pdf->preferences( -outlines => 1 )
        if $bookmark;

    $pdf->update;
    $pdf->end;
}

##</code><code>##

GSview 4.6 2004-01-11
AFPL Ghostscript 8.14 (2004-02-20)
Copyright (C) 2004 artofcode LLC, Benicia, CA.  All rights reserved.
This software comes with NO WARRANTY: see the file PUBLIC for details.
Scanning PDF file
%GSVIEW_PDF_PAGES: 1 19
Displaying PDF page 1
%GSVIEW_PDF_PAGE: 1
%GSVIEW_PDF_MEDIA: [0 0 594.9 841.36]
%GSVIEW_PDF_ROTATE: 0
Error: /invalidfont in /AB+F0
Operand stack:
   --dict:4/4(L)--   AB+F0   7.92
Execution stack:
   %interp_exit   .runexec2   --nostringval--   --nostringval--   --nostringval--   2   %stopped_push   --nostringval--   --nostringval--   false   1   %stopped_push   1   3   %oparray_pop   1   3   %oparray_pop   1   3   %oparray_pop   1   3   %oparray_pop   .runexec2   --nostringval--   --nostringval--   --nostringval--   2   %stopped_push   --nostringval--   --nostringval--   --nostringval--   --nostringval--   --nostringval--   %array_continue   --nostringval--   false   1   %stopped_push   --nostringval--   %loop_continue   --nostringval--
Dictionary stack:
   --dict:1120/1686(ro)(G)--   --dict:0/20(G)--   --dict:78/200(L)--   --dict:104/127(ro)(G)--   --dict:238/347(ro)(G)--   --dict:20/24(L)--   --dict:4/6(L)--   --dict:20/20(L)--   --dict:1/1(ro)(G)--   --dict:1/1(ro)(G)--   --dict:1/1(ro)(G)--   --dict:9/13(L)--
Current allocation mode is local
Last OS error: No such file or directory
pdf_page failed