Hans Dieter Pearcey


Pad::Tie - tie an object to lexical contexts


 Version 0.006


  use Pad::Tie;

  my $obj = MyClass->new(...);
  my $pad_tie = Pad::Tie->new(
      scalar    => [qw(fooble quux)],
      array_ref => [qw(numbers)],
      hash_ref  => [qw(lookup)],

  my $code = $pad_tie->wrap(\&bar);
  $code->(1, 2, 3);

  sub foo {
    my $fooble;

    print $fooble; # $obj->fooble

  sub bar {
    my $quux = 17; # $obj->quux(17);
    my %lookup;

    for my $key (keys %lookup) {
      # keys %{ $obj->lookup }

      $lookup{$key} ||= 1;       
      # $obj->lookup->{$key} ||= 1

    my @numbers = @_; 
    # $obj->numbers([ 1, 2, 3 ]); @_ is from above


Pad::Tie lets you use your objects' methods as though they were lexical variables.

Alternately, it lets you use lexical variables to refer to your bound object methods. It's all a matter of perspective.

Creating a Pad::Tie object requires an object (the invocant) and a list of methods (with their personalities) that will be exposed to called subroutines.

There are a number of different calling conventions for methods in Perl. In order to accommodate as many as possible, Pad::Tie lets plugins handle them. See Pad::Tie::Plugin for details on writing new method personalities.


The simplest personality. Using the variable calls the method with no arguments. Assignments to the variable call the method with a single argument, the new value.

  ... Pad::Tie->new($obj, [ scalar => [ 'foo' ] ]);

  sub double_nonzero_foo {
    my $foo;
    if ($foo) {        # $obj->foo
      $foo = $foo * 2; # $obj->foo($obj->foo * 2)



Nearly as simple as scalar. Using the variable bound to doesn't actually generate a method call; instead, it's retrieved once and the reference is used repeatedly.

  ... Pad::Tie->new($obj, [ array_ref => [ 'foo' ] ]);

  sub add_to_foo {
    my @foo;
    push @foo, @_; # push @{ $obj->foo }, @_


Reading from a array bound to a 'list' method personality calls the method with no arguments in list context. Assigning to the array calls the method once with all of the assigned values. Reading individual array elements is ok, but setting individual array elements will croak.

  ... Pad::Tie->new($obj, [ list => [ 'foo' ] ]);

  sub get_or_set_foo {
    my @foo;
    @foo = @_ if @_; # $obj->foo(@_)
    return @foo;     # $obj->foo

Because of the way this personality works, if you call the method directly or otherwise change its return values, those changes may not be reflected in bound array values.

In other words, continuing the example above, this is a bad idea:

  sub dont_do_this {
    my @foo;
    @foo = (1, 2, 3);
    $obj->foo(4, 5, 6);
    print "@foo"; # probably prints '1 2 3'


This method personality takes no arguments and makes the invocant available as $self in any called subroutine. Note that it will not add $self to the sub if it's not there; you still need a my $self declaration in the scope of the sub.

  ... Pad::Tie->new($obj, [ 'self' ]);

  sub who_am_i {
    my $self;
    return $self->name;


Each Pad::Tie object is configured with a list of methods and personalities:

  Pad::Tie->new($obj, [ $personality => \@methodnames, ... ])

The list of method names is actually just an argument to the plugin. See individual plugins and Pad::Tie::Plugin for details.

Note that this is an 'optlist'; see Data::OptList. The short version is that if you don't need arguments, such as for the self plugin, you don't need to pass an explicit undef value. See "SYNOPSIS".

More detail about methods and personalities is given above. See DESCRIPTION.


Most of the time you will only need to use new and call, or perhaps wrap. The names for call and wrap are chosen deliberately to match up with methods from Lexical::Persistence, which this module is build using.


  my $pad_tie = Pad::Tie->new($obj, \@methods);

Create a new binding for the given object.



  • subclassing

    Work out and test interactions.

  • method auto-discovery

    Provide method personality plugins for various object frameworks to avoid having to type a bunch.

  • more method personalities

    e.g. Rose::Object::MakeMethods::Generic's different kinds of hash/array accessors, a scalar that calls different methods for FETCH and STORE ($url in examples/mech.pl).

  • more options

    interface for configuring the underlying Lexical::Persistence object

  • more documentation

    examples that aren't filled with 'foo', documentation on plugins


Pad::Tie::Plugin Lexical::Persistence Devel::LexAlias PadWalker Data::OptList


Hans Dieter Pearcey, <hdp at cpan.org>


Please report any bugs or feature requests to bug-pad-tie at rt.cpan.org, or through the web interface at http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Pad-Tie. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.


You can find documentation for this module with the perldoc command.

    perldoc Pad::Tie

You can also look for information at:


Thanks to Pobox.com, who sponsored the development of this module.


Copyright 2007 Hans Dieter Pearcey, all rights reserved.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

1 POD Error

The following errors were encountered while parsing the POD:

Around line 285:

You forgot a '=back' before '=head1'