use Archive::Tar;
use strict;
my $parent = Archive::Tar->new("parent.tar");
my $child_tar = Archive::Tar->new();
$child_tar->add_data("file1",$parent->get_content("file1"));
$child_tar->add_data("file2",$parent->get_content("file2"));
$child_tar->write("child1.tar");
$parent->remove("file1");
$parent->remove("file2");
$parent->write("child2.tar");