My suggestion to you is:

1. Take a step back, think to yourself, what does this module actually do?
2. Think to yourself, am I doing a proper job of abstracting data from logic?
3. Ask: does all of this data need to be loaded at all times? Or is this the type of thing where I can make 3 or 4 dbm's and tie them at run time, so as to not have to repopulate them all the time?
4. Do I have so much data, and I foresee this growing and needing more computation, that it really should be in a relational model of some sort?
5. Does this really need to be 1 3000 line module? or should this be 1 50 line module and a series of modules that inherit the interface and special case?

Good luck! and keep asking away...

Well, to justify some of my points.

This module is huge because the data it processes is really complex. Its handling strings from another program which report up to 200 different enviromental conditions in a working environment. The string can report 0-200 of these conditions at any one time and all of the values need to be available.

Therefore, say someone wanted to know the oxygen content of the environment, they would take the environmental data string from the test equipment and send it to the module, which decodes it and returns all the factors as object variables.

If there was no oxygen data, then the variable containing its content value would be undef and there program using the module would take appropriate action to report that.

I have looked and looked again and this module and made two or three small programs, optimised to do certain tasks and then combined.

The big problems is that the whole problem requires the decoding and handling of various text strings, something I find Perl unmatched for, however the nature of the data is what is forcing the size of the module!

I'd like to use mod_perl, but never used it before and cant find any clear details on implementing it.

- Jed

whenever I hear about complex parsing, and I think about module size, performance, scalability, maintainability... I always come to the same exact conclusion... someone should check out Parse::RecDescent


There have been some awsome comments on how to use Parse::RecDescent here in the monestary, look at some of merlyn's posts... however, the quick overview is simple (if you've never worked with parsers...) Parse::RecDescent will allow you to write a grammar that describes what it is that the data should look like, and the mechanisms by which it should be dissected and manipulated. If you are having to do a lot of conditional matching (eg If this match this else match that) then it may be a perfect job for a recursive descept parser... Give it a look, the docs are awsome, and if you have questions on it, I am sure some of the more knowledgable monks (talk to maverick) will be able to give you a hand on how to dissect Parse::RecDescent. Hope it goes well!

A hundred exported variables would be a sign to me that I should seriously rethink my interface.

In more specific context, there are not two variables called "name" in memory when your module is used. Perl uses garbage collection, which is (some say) simplistically implemented by a reference count. When a variable's reference count goes to 0, it is "destroyed" and the memory it used is given back to perl - not to the system - to be reused. Assuming you haven't returned a reference to your $name, that instance of the variable was destroyed when function A exited.

It may be possible perl will reuse that memory space for Function B, or it may allocate more. I do not know how aggressive perl is in its memory recycling and it still really depends on the flow of your code and how it is used.

You can also see perldoc perlobj ( search on garbage ) for a better description of the collection algorithm.

mikfire

One detail. Lexical variables do not hand their memory back. Instead perl assumes that it will need to repopulate them again and keeps the memory in use to make it faster to allocate on the next pass through. Unfortunately this can be seen in current versions of Perl in an obscure bug when you declare a my variable inside a one-line if or unless. In particular this sort of thing is seriously unwise:

sub my_func {
    # Stuff
    my $foo = $bar unless $cond;
    # More stuff
}
[download]

Perl's behaviour in this case is IMO seriously broken, intentionally undocumented, and as Larry Wall put it, "Use of this feature would be erroneous." It is also far more complex than a simple test would indicate.

I would expect it to get fixed, probably for 5.6.2. In the meantime make sure that my statements are guaranteed to be executed.

EDIT
If anyone wants to know more about this, here is an explanation of what exactly is going on, and the original bug report. (*ahem* Yup, that is my bug.)

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Sorry, NDA's and all that! :o(

- Jed