Toby Inkster > Acme-Lexical-Thief-0.002 > Acme::Lexical::Thief

Download:
Acme-Lexical-Thief-0.002.tar.gz

Dependencies

Annotate this POD

Website

View/Report Bugs
Module Version: 0.002   Source  

NAME ^

Acme::Lexical::Thief - steal lexical variables from your caller

SYNOPSIS ^

   use 5.012;
   use strict;
   use warnings;
   use Acme::Lexical::Thief;
   
   sub greet {
      my $name = shift;
      greet_verbally();
   }
   
   sub greet_verbally {
      steal $name;  # caller variable
      say "Hello $name";
   }

DESCRIPTION ^

This package allows you access to your caller's lexical variables, without them knowing! Full read/write access. This is generally a pretty bad idea, hence the Acme namespace.

You can steal scalars, arrays and hashes:

   steal $car, @treasures, %stash;

Parentheses can surround the list of variables to steal:

   steal ($car, @treasures, %stash);

Generally everything should "just work" as you expect it to. Except when it does not.

Technically speaking, your stolen $car is a package-scoped (our) variable which is lexically aliased (local *car) to the caller's variable of the same name. Because steal is parsed at compile-time, you don't need to (and indeed should not!) pre-declare your stolen variables.

   sub greet_verbally {
      my $name;   # don't do this!
      steal $name;
      say "Hello $name";
   }

By default, this module steals from your immediate caller. You can thieve higher up the call stack using:

   steal 0 ($car);  # caller's $car
   steal 1 @boats;  # caller's caller's @boats
   steal 2 %stash;  # caller's caller's caller's @stash

You cannot indicate the level you wish to steal from using a variable; it must be a literal integer in your source code. (It can be in decimal, octal, hexadecimal or binary notation.) The integer must immediately follow the steal keyword, and not be followed by a comma.

The steal keyword cannot be used in an expression; it must be a standalone statement.

   steal $foo;
   if (defined $foo) { ... } # ok
   
   if (steal $foo) { ... }   # not this!
   
   # this works...
   if (do { steal $foo; defined $foo })
   {
      # ... but $foo won't exist in this block!
      ...
   }

If you attempt to steal a variable which does not exist, then a run-time exception will be thrown.

WHY YOU SHOULD NOT USE THIS MODULE ^

When people declare lexical (my) variables within a sub, they (quite reasonably) expect these to stay local to the sub. If they rename those variables, change them (say replacing a hashref with a hash), drop them or whatever, then they don't expect code outside the sub to pay much attention.

Peeking at your caller's lexicals breaks those expectations.

Peeking at your caller's lexicals leaks an abstraction.

Peeking at your caller's lexicals can cause spooky action at a distance.

Every time you peek at your caller's lexicals, a fairy dies.

Just think about that for a minute, won't you?

BUGS ^

Please report any bugs to http://rt.cpan.org/Dist/Display.html?Queue=Acme-Lexical-Thief.

SEE ALSO ^

PadWalker - a slightly more sane alternative to peeking at your caller's lexicals.

Data::Alias - a slightly more sane way of creating lexical aliases.

This package was initially published on PerlMonks as Acme::Asplode http://www.perlmonks.org/?node_id=1008814, but I prefer the current name.

AUTHOR ^

Toby Inkster <tobyink@cpan.org>.

COPYRIGHT AND LICENCE ^

This software is copyright (c) 2012 by Toby Inkster.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

DISCLAIMER OF WARRANTIES ^

THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.

syntax highlighting: