Perhaps Scalar::Util's blessed() is a better check for objectness.

I ran the following code and all tests pass under Perl 5.8.2. Odd.

#!/usr/bin/perl -w

use strict;

package Foo;

use strict;
use vars '$VERSION';
$VERSION = 1;

package main;

use Test::More tests => 4;

my $foo = bless {}, 'Foo';
isa_ok( $foo, 'UNIVERSAL' );
ok( UNIVERSAL::isa( 'Foo', 'UNIVERSAL' ) );

@Foo::ISA = ();

isa_ok( $foo, 'UNIVERSAL' );
ok( UNIVERSAL::isa( 'Foo', 'UNIVERSAL' ) );
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