use Scalar::Util qw(blessed);

if (my $class=blessed $foo) {
  print "Its an object of class $class\n";
} else {
  print "Its not an object\n";
}

##</code><code>##

#!perl -l
use Scalar::Util qw(blessed reftype refaddr);
use overload;
*isa=*UNIVERSAL::isa;
*StrVal=*overload::StrVal;

my $array=[];
my $Array=bless [],'ARRAY';
my $hash={};
my $Evil_Hash=bless {},'ARRAY';


foreach my $name (qw($array $Array $hash $Evil_Hash)) {
	my $ref=eval $name;
	print "Testing '$name'";
	print "ref      :",ref $ref;
	print "U::isa   :",isa($ref,'ARRAY');
	print "->isa    :",eval { $ref->isa('ARRAY') } || do{ chomp($e=$@); $e};
	print "StrVal   :",StrVal($ref);
	print "blessed  :",blessed($ref);
	print "reftype  :",reftype($ref);
	print "refaddr  :",refaddr($ref);
	print "----"
}
__END__
Testing '$array'
ref      :ARRAY
U::isa   :1
->isa    :Can't call method "isa" on unblessed reference at D:\Temp\blessed.pl line 18.
StrVal   :ARRAY(0x1ab25f0)
blessed  :
reftype  :ARRAY
refaddr  :27993584
----
Testing '$Array'
ref      :ARRAY
U::isa   :1
->isa    :1
StrVal   :ARRAY=ARRAY(0x1ab25d8)
blessed  :ARRAY
reftype  :ARRAY
refaddr  :27993560
----
Testing '$hash'
ref      :HASH
U::isa   :
->isa    :Can't call method "isa" on unblessed reference at D:\Temp\blessed.pl line 18.
StrVal   :HASH(0x1abf0b8)
blessed  :
reftype  :HASH
refaddr  :28045496
----

##</code><code>##

Testing '$Evil_Hash'
ref      :ARRAY
U::isa   :1
->isa    :1
StrVal   :ARRAY=HASH(0x1abf1a8)
blessed  :ARRAY
reftype  :HASH
refaddr  :28045736
----