You seem to be running this as a CGI script... so you might want to look in the webserver's error_log, because (AFAIK) the debug prints will go to STDERR.

Alternatively, redirect STDERR to STDOUT, so the debug messages will also be sent to the browser.  I.e. modify your script as follows:

#!/usr/bin/perl

use warnings;
use strict;

use CGI qw(:standard);
use CGI::Carp qw(fatalsToBrowser carpout);

carpout(\*STDOUT);

...
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