#!/usr/bin/perl

package test_package;

use strict;
use warnings;

sub new { return bless {}; }

sub test_function { print "Original test_function! $_[1]\n"; }

sub loader {
  eval($_[1]);
  warn "ERROR: $@\n" if ( $@ );
}

package main;

use strict;
use warnings;

my $counter = 0;

my $f = new test_package();

$f->test_function($counter++); # 1

# "backup" the test_function method 
$f->loader('*test_package::new_test_function = \&test_package::test_function;');
$f->new_test_function($counter++);

# Overwrite the existing "test_function" subroutine
$f->loader("package test_package; sub test_function { print \"New output! \$_[1]\n\"; } 1;");

# Should see two different outputs
$f->test_function($counter++);
$f->new_test_function($counter++);

# "Restore" the test function from it's "backup"
$f->loader("*test_package::test_function = *test_package::new_test_function;");
$f->test_function($counter++);

##</code><code>##

Original test_function! 0
Original test_function! 1
Subroutine test_function redefined at (eval 2) line 1.
New output! 2
Original test_function! 3
Original test_function! 4