How Do I Bundle Perl Modules and Their Tests Into the Same File?

perlknight has asked for the wisdom of the Perl Monks concerning the following question:

All, in python you can write a module and declare package main to test it. Can something like this be done in perl? e.g:

package abc;
come code...
package main
some test code for this module
[download]

Thanks.

2006-02-13 Retitled by Steve_p, as per Monastery guidelines
Original title: 'Can this be done...'