perl_closure_change_test.pl

package MasterableThing;

use Moose;

has 'something' => (is => 'rw', isa => 'Str');
has 'master' => (is => 'rw');

sub do_this_thing {
	my $themaster =  $_[0]->master;
	my $theoriginal = $_[0];
	$_[0] = $themaster if defined $themaster;
	my $code = $_[1];
	$code->(@_[2 .. -1]);
	$_[0] = $theoriginal;
	return 1;
}

package main;

use MasterableThing;

sub main {
	my $master_thing = MasterableThing->new(
		something => 'master thing something',
	);
	my $slave_thing = MasterableThing->new(
		something => 'slave thing something',
		master => $master_thing,
	);

	my $thing = $master_thing;
	print "thing is master thing: " . $thing->something ."\n";
	$thing->do_this_thing(sub { print "doing this thing with: " . $thing->something . "\n"; });
	print "thing is now: " . $thing->something . " something\n";

	print "\n";

	$thing = $slave_thing;
	print "thing is slave thing: " . $thing->something ."\n";
	$thing->do_this_thing(sub { print "doing this thing with: " . $thing->something . "\n"; });
	print "thing is now: " . $thing->something . " something\n";
}

main();

# results:
#
# thing is master thing: master thing something
# doing this thing with: master thing something
# thing is now: master thing something something
# 
# thing is slave thing: slave thing something
# doing this thing with: master thing something
# thing is now: slave thing something something