# here's the pre portion...
my $count;
my %data;

IterateOver::file({
  loop => sub {
    if (/^(.*?)\s*=\s*(.*?)\s*(?:#.*)$/)
    {
      $data{$1} = $2;
    }
  },
  $some_file
 );

# post goes here...

##</code><code>##

my @files = ( ... );
my $count;
my %data;
IterateOver::files({
  pre => sub {
    print "Starting on file $_.\n";
    $count = 0;
  },
  loop => sub {
    if (/^[^#]/ and /^(.*?)\s*=\s*(.*?)\s*(?:#.*)$/)
    {
      $data{$1} = $2;
      ++$count;
    }
  },
  post => sub {
    print "Found $count keys in $_.\n";
    print "Total unique keys so far: ", scalar keys %data, "\n";
  },
  @files
 );

##</code><code>##

package TaskFilter;

use base 'Task';

sub prefilter
{ 1 } # default pre is to do nothing and succeed at it.

sub postfilter
{ 1 } # same thing

sub filter
{ die "need to implement filter in subclass '" . ref $_[0] . "'\n"; }

sub get_object_list
{
  # generic implementation common to all my tasks derived from here.
}

sub sort_object_list
{
  # to allow subclass to change order if needed.
  sort @_
}

sub perform_task {
  my $self = shift;
  $self->prefilter() or die "prefilter failed.";

  my @records = $self->sort_object_list($self->get_object_list());
  for my $r (@records)
  {
    $self->filter($r);
  }

  $self->postfilter() or die "postfilter failed.";
  1;
}

1;