Metaprogramming

Hi fwp,

once again, I'm thinking about some borderline fun with perl. 
"Borderline" because of the buzzword in the subject line that should 
repel all but the sickest and the .com types. (Now, which would I be?)
I've been wondering whether it is possible to implement some kind of 
mechanism that allows a Perl script to modify itself at runtime. 
Performance is not an issue as this isn't anything you'd want to use in 
production code. :)
So far, I see no way of achieving this. Using source filters, one may 
modify the source at compile-time and in fact I spent an hour doing so. 
(For a good reason, I never used source filters before, so it took me a 
bit to write that code.)
The result is Acme::Metification. Horrible name for a horrible hack.
http://search.cpan.org/author/SMUELLER/Acme-Metification-1.00/

Since the last upload, I have modified the module so you can define 
markers relative to which the positions of the "meta*" commands are 
interpreted. Additionally, I *should* be able to allow the functions to 
accept line numbers at run-time. (eg "meta marker $startline, $endline)
I would do that by inserting code for the meta command that determines 
$startline and $endline at runtime and evaluates the corresponding 
lines. (The code would have been originally generated in the lexical 
scope of the original array of code lines in the source filter.) Of 
course, in order to allow recursive "metaprogramming", one'd have to 
filter the code-to-be-evaluated first and apply the same transformations 
that were done to the rest of the source if necessary. (Which is a pain 
to implement but nevermind.)
I suppose I have successfully twisted most of your brains with that 
paragraph of bad english and bad ideas. ;)
What I am really interested in is a few better ideas on how one could go 
about implementing some concept of LISP-like metaprogramming for Perl. 
Any better ideas than the above?
Steffen
--
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