#!/usr/bin/env perl -l

use strict;
use warnings;

{
    local $/ = '';

    while (<DATA>) {
        chomp;
        print '--- One Block ---';
        print;
    }
} 

__DATA__
Block1 Line1
Block1 Line2
Block1 Line3


Block2 Line1
Block2 Line2
Block2 Line3



Block3 Line1
Block3 Line2
Block3 Line3

Block4 Line1
Block4 Line2
Block4 Line3

##</code><code>##

--- One Block ---
Block1 Line1
Block1 Line2
Block1 Line3
--- One Block ---
Block2 Line1
Block2 Line2
Block2 Line3
--- One Block ---
Block3 Line1
Block3 Line2
Block3 Line3
--- One Block ---
Block4 Line1
Block4 Line2
Block4 Line3

##</code><code>##

    $line = $z->getline();
    $line = <$z>;

##</code><code>##

my $z = IO::Uncompress::Bunzip2::->new($filename);

{
    local $/ = '';

    while (<$z>) {
        ...        
    }
}