Can't use an undefined value as a symbol reference with mod

nysus has asked for the wisdom of the Perl Monks concerning the following question:

The following code snippet works fine when run out of the cgi-bin:

  my $pdf = new PDF::Labels(
      $PDF::Labels::PageFormats[0],
      filename=>'files/labels.pdf',
  );
[download]

However, when I use this code from within subroutine in a package in my mod_perl application, I get the following error:

Can't use an undefined value as a symbol reference at /usr/local/share
+/perl/5.20.2/PDF/Create.pm line 63.\n, referer: http://mydomain.com/i
+ndex.pl
[download]

Not sure how to go about fixing this. I'm new to mod_perl.

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Comment on Can't use an undefined value as a symbol reference with mod_perl Select or Download Code

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Re: Can't use an undefined value as a symbol reference with mod_perl by kennethk (Abbot) on Sep 24, 2015 at 15:38 UTC
<shot in the dark> Try the code: `my $pdf = PDF::Labels->new( $PDF::Labels::PageFormats[0], filename=>'files/labels.pdf', );` [download] Not quite sure why this might happen, but the error condition is saying that perl thinks you are trying to use something as a filehandle that doesn't have a value. </shot in the dark> It's also possible that the actual error is happening in the `PDF::Labels` `new` routine and someone is croaking it up to the invocation you are seeing. This would make sense, as you are passing in a filename, so maybe an open is failing and someone forgot to test it for success. That failure, in turn, could be due to a permissions problem, which could definitely result in a weird inconsistency between CGI and mod_perl. #11929 First ask yourself `How would I do this without a computer?' Then have the computer do it the same way.	[reply] [d/l] [select]
Re^2: Can't use an undefined value as a symbol reference with mod_perl by nysus (Parson) on Sep 24, 2015 at 15:53 UTC
OK, I changed the path to start from the root directory and that fixed the problem. So instead of files/labels.pdf I'm using /var/www/vt/files/labels.pdf. Thanks!	[reply]
Re^3: Can't use an undefined value as a symbol reference with mod_perl by kennethk (Abbot) on Sep 24, 2015 at 16:10 UTC
That's a pathing problem rather than a permissions problem. It's probably worth figuring out what the mod_perl working directory is. Cwd #11929 First ask yourself `How would I do this without a computer?' Then have the computer do it the same way.	[reply]