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From: PerlFAQ Server on 9 Jul 2010 18:00
This is an excerpt from the latest version perlfaq7.pod, which
comes with the standard Perl distribution. These postings aim to
reduce the number of repeated questions as well as allow the community
to review and update the answers. The latest version of the complete
perlfaq is at http://faq.perl.org .

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7.26: How can I find out my current or calling package?

(contributed by brian d foy)

To find the package you are currently in, use the special literal
"__PACKAGE__", as documented in perldata. You can only use the special
literals as separate tokens, so you can't interpolate them into strings
like you can with variables:

my $current_package = __PACKAGE__;
print "I am in package $current_package\n";

If you want to find the package calling your code, perhaps to give
better diagnostics as "Carp" does, use the "caller" built-in:

sub foo {
my @args = ...;
my( $package, $filename, $line ) = caller;

print "I was called from package $package\n";
);

By default, your program starts in package "main", so you should always
be in some package unless someone uses the "package" built-in with no
namespace. See the "package" entry in perlfunc for the details of empty
packages.

This is different from finding out the package an object is blessed
into, which might not be the current package. For that, use "blessed"
from "Scalar::Util", part of the Standard Library since Perl 5.8:

use Scalar::Util qw(blessed);
my $object_package = blessed( $object );

Most of the time, you shouldn't care what package an object is blessed
into, however, as long as it claims to inherit from that class:

my $is_right_class = eval { $object->isa( $package ) }; # true or false

And, with Perl 5.10 and later, you don't have to check for an
inheritance to see if the object can handle a role. For that, you can
use "DOES", which comes from "UNIVERSAL":

my $class_does_it = eval { $object->DOES( $role ) }; # true or false

You can safely replace "isa" with "DOES" (although the converse is not
true).



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