Corion, below is what I see: The code I run:

#!/usr/bin/perl
##!/comptel/ccacp/elink/common/6.3/perl/bin/perl
use strict;
use warnings;
#use diagnostics;
use CGI;
use CGI::Carp 'fatalsToBrowser';
use Data::Dumper;
print Dumper(\%hash);
print Dumper($ref);

my $sqlfile  = '/var/www/cgi-bin/dual.sql';

my $q = new CGI;
my $connstr = 'id971934/colecsp@ECSP';;
my $msg = qx"sqlplus -s $connstr \@$sqlfile";

print $q->header,$q->start_html,
$q->pre($msg),$q->end_html;

cat /var/www/cgi-bin/dual.sql
select SYSDATE from dual;
exit;
[download]

********************** This script was working properly & was giving proper results(sysdate). But when I introduced "Data::Dumper", and I try to run it from command line I get below messages

[ccacp@el2310 cgi-bin]$ perl monkey.pl
Status: 500
Content-type: text/html

<h1>Software error:</h1>
<pre>Global symbol &quot;%hash&quot; requires explicit package name at
+ monkey.pl line 9.
Global symbol &quot;$ref&quot; requires explicit package name at monke
+y.pl line 10.
Execution of monkey.pl aborted due to compilation errors.
</pre>
<p>
For help, please send mail to this site's webmaster, giving this error
+ message
and the time and date of the error.

</p>
[Fri Mar 18 17:41:22 2016] monkey.pl: Global symbol "%hash" requires e
+xplicit package name at monkey.pl line 9.
[Fri Mar 18 17:41:22 2016] monkey.pl: Global symbol "$ref" requires ex
+plicit package name at monkey.pl line 10.
[Fri Mar 18 17:41:22 2016] monkey.pl: Execution of monkey.pl aborted d
+ue to compilation errors.
[download]

************************** On running from web browser, I see HTTP 500 error with message "the website cant be displayed".