I do it like I do it in Pod::Stripper and HTML::LinkExtractor. Here's the jist of it

package Buttersquash;
sub foo { 'bar' }
sub bar { 'foo' }

package main;
unless(caller()){
    print "1..3\n";
    print "ok 1\n";
    print "not " if  Buttersquash->foo ne 'bar';
    print "ok 2\n";
    print "not " if  Buttersquash->bar ne 'foo';
    print "ok 3\n";
}

=head1 SELF CONTAINED TEST

If you already installed this, simply run this oneliner

# on nix
    perl -MButtersquash -e' exec $^X, $INC{q[Buttersquash.pm]}'

# on windows
    perl -MButtersquash -e" exec $^X, $INC{q[Buttersquash.pm]}"

or simply

    perl Buttersquash.pm

=cut
[download]

Other already available options is Test::Inline (formerly Pod::Tests) by our favorite b*#@! Schwern ;)

MJD says you can't just make shit up and expect the computer to know what you mean, retardo! ** The Third rule of perl club is a statement of fact: pod is sexy.