Constant functions in POE modules

Hi,

I just found out that the implementation of POE uses constant functions a 
lot. Hey, that's an exceptional quality! There is an experimental module 
called Package::Transporter, which aids in managing constant functions.
Comparison between existing definitions, taken from lib/POE/NFA.pm:

 	sub SELF_RUNSTATE       () { 0 }
 	sub SELF_OPTIONS        () { 1 }
 	sub SELF_STATES         () { 2 }
 	sub SELF_CURRENT        () { 3 }
 	sub SELF_STATE_STACK    () { 4 }
 	sub SELF_INTERNALS      () { 5 }
 	sub SELF_CURRENT_NAME   () { 6 }
 	sub SELF_IS_IN_INTERNAL () { 7 }

And the definition with Package::Transporter:

 	use Package::Transporter sub{eval shift}, sub {
         	$_[0]->array_indices('SELF_', [],
                 	qw(RUNSTATE  OPTIONS  STATES  CURRENT  STATE_STACK
 	                INTERNALS  CURRENT_NAME  IS_IN_INTERNAL));
 	};

The convenience function array_indices automates the enumeration, which is 
a subtle feature: by using constant functions for array 
indices or hash keys, the source for structural errors can be moved
into one place (where the functions are defined). That is definitely an 
improvement. But only automation actually eliminates the source, which can 
be seen as the motivation behind Package::Transporter.

Implicit sharing of constant functions (and other definitions like 
automatically generated accessors) across packages is also supported by 
Package::Transporter. Either along the package hierarchy (stop at every :: 
and look if there are public definitions) or along the package names in 
@ISA. The latter practically means that inheritance is available for 
methods as well as attributes, even if the object is an array reference.

I'm not implying to migrate POE to Package::Transporter. Again, it's 
experimental and by default refuses to install from the CPAN shell for 
that reason. But the first lines of POE modules look very much like my 
modules did before Package::Transporter. So I thought it would be of 
general interest to you.


Thanks for POE and keep up the excellent work.


-Winfried