#! /usr/bin/perl -w
use strict;

sub blocks {
  my $fh = shift;
  my $blocksize = shift || 8192;
  sub {
    return unless read $fh, my($block), $blocksize;
    return $block;
  }
}

sub records {
  my $blocks = shift;
  my $terminator = @_ ? shift : quotemeta($/);
  my @records;
  my ($buf, $finished) = ("");
  sub {
    while (@records == 0 && ! $finished) {
      if (defined(my $block = $blocks->())) {
        $buf .= $block;
        my @newrecs = split /($terminator)/, $buf;
        while (@newrecs > 2) {
          push @records, shift(@newrecs).shift(@newrecs);
        }
        $buf = join "", @newrecs;
      } else {
        @records = $buf;
        $finished = 1;
      }
    }
    return shift(@records);
  }
}

my $iter_block = blocks(\*DATA, shift || 10);
my $iter_record = records($iter_block, "(?:foo\n)+");
while (my $record = $iter_record->()) {
  print "GOT A RECORD:\n$record\n";
}

__DATA__
hello
foo
foo
foo
world
foo
foo
foo
!