Use IO::Scalar and pass it a reference to your unbzip2'ed data (tested):

#!/usr/bin/perl -w
use strict;
use Compress::Bzip2;
use Archive::Tar;
use IO::Scalar;
use Data::Dumper;
$Data::Dumper::Indent = 1;

my $file = shift or die "usage: $0 filename.tar.bz2\n";

my $bz = bzopen($file,"r") or die;
my ($out, $buf);
$out .= $buf while $bz->bzread($buf) > 0;

my $fh = IO::Scalar->new(\$out);

my $tar = Archive::Tar->new;
$tar->read($fh) or die "Cannot read from \$fh";
my @fileinfo = $tar->list_files([qw(name size)]);
print Dumper(\@fileinfo);
[download]

--shmem

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