The disapproved manner ... check this thread A few Perl OOP questions. for more info. I'll leave it at that. ;-)

The caller thing - I'm not sure about speed. But I don't see caller used very often, so it's probably not well understood. That said, I merely mentioned the way I'd normally approach the problem and did not mean to imply that yours was inferior. There's "clever" and "too clever". Where the line is drawn, however, depends on one's experience ;-)

Here's what I think a reasonable usage of this paradigm would look like from the caller's perspective. Note that this is not intended to be the only reasonable usage, just an example of one reasonable usage:

# 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...
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Thus, the example:

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
 );
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Don't get me wrong, I've done this in an object in perl. But that's because I was part of a framework, and my framework was already object oriented (oddly enough, this is the third time today I've talked about TaskManagers and Tasks). I have a package that does iteration over some common data, and then calls object methods (not passed in but predefined) as hooks into various parts of the loop - including pre-filter, filter, and post-filter. There's no need to pass in callbacks because the loop function is inside another module dedicated to this task. It looks something like this (see above for the layout of Task):

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;
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Does that help?