I usually use Scalar::Util::blessed. Never failed me so far. Would your approach work with autobox?

Update: Your suggested solution has a (nearly obvious) pitfall: 

sub Foo::isa { die "bla" };
my $ref = bless {}, 'Foo';

eval { $ref->isa() };
if ($@) {
    print "Not an object\n";
}
else {
    print "An object\n";
}

[download]

Also in general this construct: 

eval { ... }
if ($@) { ... }

[download]

Isn't all that reliable because a DESTROY sub might clear $@ accidentally. Rather use 

if (eval {...; 1}){ ... }

[download]

Instead (Ok, this is nit-picking, but you asked for reliability...).

In reply to Re: To be, or not to be, an object ? by moritz
in thread To be, or not to be, an object ? by Bloodnok

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