# in Alpha.pm

   sub sayhowdy {
     my $self = shift;
     my $string = q{};
     open my $fh, ">", \$string;
     print $fh "Howdy, alpha\n";
     close $fh;
     return $string;
   }

   # in Beta.pm

   sub sayhowdy {
     my $self = shift;
     my $string = q{};
     open my $fh, ">", \$string;
     print $fh "Howdy, beta\n";
     close $fh;
     return $string;
   }

##</code><code>##

   *Alpha::sayhowdy = \&sayhowdy if ! defined &Alpha::sayhowdy;

##</code><code>##

   use Test::More qw( no_plan);

   use_ok( q{Alpha} );

   my $class = q{Alpha};
   my $self = $class->new();

   isa_ok($self, $class);
   can_ok($class, q{sayhowdy} );

   is($self->sayhowdy(), qq{Howdy, alpha\n},
       "alpha sayhowdy okay");

   undef &Alpha::sayhowdy;
   eval { $self->sayhowdy(); };
   like($@, qr/^Undefined subroutine &Alpha::sayhowdy called/,
       "Alpha::sayhowdy() is now undefined");


   require_ok('Beta');
   is($self->sayhowdy(), qq{Howdy, beta\n},
       "Beta::sayhowdy is now Alpha::sayhowdy");

##</code><code>##

   [Alpha] 539 $ prove -vb t/03_gamma.t
   t/03_gamma....ok 1 - use Alpha;
   ok 2 - The object isa Alpha
   ok 3 - Alpha->can('sayhowdy')
   ok 4 - alpha sayhowdy okay
   ok 5 - Alpha::sayhowdy() is now undefined
   ok 6 - require Beta;
   ok 7 - Beta::sayhowdy is now Alpha::sayhowdy
   1..7
   ok
   All tests successful.
   Files=1, Tests=7,  0 wallclock secs

##</code><code>##

   $ cover -delete
   $ make test HARNESS_PERL_SWITCHES=1
   $ cover cover_db --report=txt > coverage.txt

   # in the section of coverage.txt reporting on lib/Beta.pm:
   # (for simplicity, displaying only statement coverage)

   blib/lib/Beta.pm

   line  err   stmt   code
   1                  package Beta;
   2                  #$Id#
   3              2   use strict;

   # [snip]

   16             2       print $fh "Howdy, beta\n";
   17             2       close $fh;
   18             2       return $string;
   19                 }
   20
   21                 *Alpha::sayhowdy = \&sayhowdy
                          if ! defined &Alpha::sayhowdy;
   22
   23                 1;