{
  my $offset;
  sub build_data {
    seek DATA, ($offset ||= tell DATA), 0;
    return [ <DATA> ];
  }
}
[download]

_____________________________________________________
Jeff[japhy]Pinyan: Perl, regex, and perl hacker, who'd like a job (NYC-area)
s++=END;++y(;-P)}y js++=;shajsj<++y(p-q)}?print:??;

Thank you! It hadn't occurred to me that the value landing in my $offset could persist through every time I entered the package to use its sub. Much less am I aware of the true workings of __DATA__ and using seek & tell to play with it. :-)

As for "fast food", I'd say about 1% of the main program's data is accessed this way, 99% comes in traditional fat free ways. But "needs of the business" seem to require accessing this particular chunk of data in a more devious way... Are there side effects I should be aware of if I operate in this way? Besides its just being creepy?

The value sticks around because I don't create in the function, but in the scope surrounding the function. If you've got Perl 5.6, here's a cooler way to do it:

{ 
  my $offset;
  CHECK { $offset = tell DATA }
  sub data { seek DATA, $offset, 0; [<DATA>] }
}
[download]

The CHECK block happens just after compile-time ends.

_____________________________________________________
Jeff[japhy]Pinyan: Perl, regex, and perl hacker, who'd like a job (NYC-area)
s++=END;++y(;-P)}y js++=;shajsj<++y(p-q)}?print:??;

This is a case for applying tye's best practices:

{
  my $offset;
  BEGIN { $offset = tell DATA }
  sub build_data {
    seek DATA, $offset, 0;
    return [ <DATA> ];
  }
}
[download]

That way, even if someone else touches DATA before build_data is called the first time (aka a race condition), it still produces the correct result.

Update: Good point - I stand corrected.

Makeshifts last the longest.

You cannot use BEGIN there. See my response earlier, where I do a very similar solution. I use CHECK instead (because Perl has not seen the __DATA__ marker yet, if you use BEGIN).

_____________________________________________________
Jeff[japhy]Pinyan: Perl, regex, and perl hacker, who'd like a job (NYC-area)
s++=END;++y(;-P)}y js++=;shajsj<++y(p-q)}?print:??;

$offset = tell DATA and seek DATA, $offset, SEET_SET. It's just a filehandle - reset it's position when you need to.

__SIG__
use B;
printf "You are here %08x\n", unpack "L!", unpack "P4", pack
  "L!", B::svref_2object(sub{})->OUTSIDE;
[download]

If you jump back to the beginning, just take care not to jump too far, because otherwise you will get the sourcecode of the script as "DATA", e.g. the following script prints its own sourcecode...

#! /usr/bin/perl
seek (DATA,0,0);
print <DATA>;
__DATA__
warn "Just another perl hacker\n";
[download]

Best regards,
perl -e "s>>*F>e=>y)\*martinF)stronat)=>print,print v8.8.8.32.11.32"

Tou might also want to use Inline::File if you want to use DATA as a file.

Just a related question ...

Is is manditory to have all the __DATA__ at the bottom of the script.

if it can be placed in the middle of script,

how to differentiate the "__DATA__ content" form the program script?

Can someone describe/elobrate/comment about the __DATA__ usage, its constraints and best practices..

Thanks in advance

Anandatirtha

Basically, __DATA__ provides a quickie way to bundle data for a script right there at the bottom of the script, and make it available to you via the filehandle <DATA>, rather than have to (lazy-speak) put the data in a text file and make sure you always have access to that file, open it, etc. All text after a line containing '__DATA__ will be ignored in terms of executable code. __END__ functions similarly. Usually (?)this is for including test data for your script.

In looking for online documentation about __DATA__, the best I could find was contained in a couple of paragraphs from perldata.html (using ActiveState) which in turn said "See the SelfLoader manpage for more description of __DATA__, and an example of its use." Not that said description was crystal clear... Good Luck! :-)