$attached = attach_var($target_ref, $attach, [$optional_name]);
$attached = attached($target_ref, [ $optional_name ]);
$attached = unattach_var($target_ref, [ $optional_name ]);


# A few trivial examples. 
sub elements(\@$){
    my ($ref,$size) = @_;
    $size = 1 unless $size;
    my $info = attached($ref,'elements') || attach_var($ref,[0,$size],'elements');

    my @ret = ();

    if( $info->[0] >= @$ref ) {
      unattach_var($ref,'elements');
      return;
    }else{
      @ret = @{$ref}[$info->[0]..($info->[0]+$info->[1] -1)];
      $info->[0]+= $info->[1];
    }
    @ret;
}

while( my @els = elements(@large_array,4) ){  
    # Process non destructively
}

# Lazily generate a span of integers.
sub int_span($$){
    my $info = attached(\$_[0],'INT_SPAN') || attach_var(\$_[0],[$_[0],$_[1] ],'INT_SPAN');
    unattach_var(\$_[0],'INT_SPAN') and return  if $info->[0] >  $info->[1];
    return $info->[0]++;
}

while(my $i = int_span(1,1000000000)){
  print $i,"\n";
}

##</code><code>##

# Persistant subroutine data
sub somesub {
    my $p_args = attached(\&somesub,'somesub') || attach_var(\&somesub,{called=>0},'somesub'); 
    ++$p_args->{called};
    # The persistant arg hash could be keyed on the caller info if desired
    # for context sensitivity
}