[Petal] compiled expressions

[Fergal Daly]

Hi,
	I've got fully compiled expressions and all tests passing. To play with it, 
apply the patches from earlier today then install the 2 modules from

http://www.fergaldaly.com/computer/Text/

Doing a use Petal::Teng, it sets

$Petal::CodeGenerator = "Petal::Teng::CodeGenerator"

Advantages:

* triple speed for my sample template, everything is compiled down to Perl, 
nothing is parsed or interpretted at runtime

* new syntaxes allowed

this/method person/name

which will do roughly

$hash->{this}->method($hash->person->{name})

and 

this{key}[5]

which translates to

$hash->{this}->{key}->[5]

which is much faster than using / if you know the types of your variables in 
advance.


Problems:

* the generated code is a bit ugly due to no indentation

* modifiers are handled by reverting to doing a $hash->get("modifer:blah") - 
this is unavoidable until modifiers know about compiled expressions

* the parser was originally built for TALES so there may be some places where 
Petales differs that I have yet to find.

* you may get warnings about undefined values when you access undefined values 
in the hash. Petal used to suppress these warnings. This is particularly 
noticeable when running test 031 as it accesses a lot of undef values.

Apart from that, everything should work (although it is still experimental), 
if it doesn't please let me know,

F