Ah yes. I had never made a source filter before, so I tried my fingers at a little hack. It has some obvious defects, but it works on the little example. It also uses Data::Lazy. Note how laziness of evaluation plays tricks with us here in the last example. Use only if you know what you are doing. Here is the simple module: 
package LazyFilt;

use 5.8.0;
use warnings;
use strict;
use Data::Lazy;
use Filter::Util::Call;

our $state = 0;

sub import {
  filter_add([]);
}

sub filter {
  my $status = filter_read();
  return $status unless $status > 0;
  my $result = "";
  my @stmts = split /;/;
  foreach my $stmt (@stmts) {
    my @lazyass = split /=\[l\]/,$stmt;
    if (@lazyass == 1) {
      $result .= $stmt . ";";
      next
    }
    die "We don't support this (@lazyass)!" if (@lazyass > 2);
    $result .= "tie $lazyass[0], 'Data::Lazy', sub { $lazyass[1] };";
  }
  $result .= "\n";
  $_ = $result;
  return $status;
}

1;

[download]
And a small example that uses it: 
use LazyFilt;
use strict; 
use warnings;

sub calc { 
  my ($p1,$p2,$p3) = @_;
  print "Here is where really slow stuff happens\n";
  my $sum = $p1 + $p2;
}

my $result =[l] calc(30,20,"FooBar");
my $result2 =[l] calc($result,20,"YoYo");
print "Just about now I need to show the first result: $result\n";
my $result3 = $result + $result2;
print "And now I need the whole result: $result3 \n";
print "After this it is free to poke around: $result2\n";

my $a = 10;
my $result4 =[l] 2+$a;
$a = 14;
print "Result? $result4\n";

[download]
If anyone actually fancies this I could even clean it up properly.

In reply to Re: Re: Re: What could I do with just Perl? by dref
in thread What could I do with just Perl? by Cody Pendant

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