Am I correct in saying that this perhaps is because the object I m trying to print to string is not the correct type?
No, its because you don't have an object, observe

#!/usr/bin/perl --

use strict;
use warnings;
use diagnostics;

use CGI();

my $cgi = CGI->new();
my $poop = [];

$cgi->header;
$poop->nonsense;
__END__

Can't call method "nonsense" on unblessed reference at temp.pl line 13
+ (#1)
    (F) A method call must know in what package it's supposed to run. 
+ It
    ordinarily finds this out from the object reference you supply, bu
+t you
    didn't supply an object reference in this case.  A reference isn't
+ an
    object reference until it has been blessed.  See perlobj.

Uncaught exception from user code:
        Can't call method "nonsense" on unblessed reference at temp.pl
+ line 13.
 at temp.pl line 13
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If you don't know what you have, you can use Data::Dumper to find out, example

#!/usr/bin/perl --

use strict;
use warnings;
use diagnostics;

use CGI();

my $cgi = CGI->new();
my $poop = [];

use Data::Dumper;
print Dumper( $cgi, $poop );

__END__
$VAR1 = bless( {
                 '.parameters' => [],
                 'use_tempfile' => 1,
                 '.charset' => 'ISO-8859-1',
                 '.fieldnames' => {},
                 'param' => {},
                 'escape' => 1
               }, 'CGI' );
$VAR2 = [];
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