{
package Foo;
use Scalar::Util 'blessed';

sub _process_calling_convention
{
	# discard pkg name, if called as class method:
	@_ && !ref($_[0]) && $_[0] eq __PACKAGE__ and shift;
	# return object, if called as object method:
	@_ && (blessed($_[0])||'') eq __PACKAGE__ ? shift : ()
}

sub bar
{
	my $obj = &_process_calling_convention;

	if ( defined $obj )
	{
		print "called as object method $obj->( @_ )\n";
	}
	else
	{
		print "called as function ( @_ )\n";
	}
}

}

# main: test:

my $x = bless {}, 'Foo';

print "\nplain module function call:\n";
Foo::bar();
Foo::bar("arg");

print "\nclass method call:\n";
Foo->bar();
Foo->bar("arg");

print "\nobject method call:\n";
$x->bar();
$x->bar("arg");