G'day Lotus1,

[Firstly, I'm a bit late to the party with this. I started to write some code yesterday, was interrupted, and only got back to it about 24 hours later.]

"This seems likely to break in future use."

There are a number of issues, especially if you were hoping to turn this into a general solution. Here are the main ones as I see them. I acknowledge that, in some cases, I'm repeating what others have already said.

• CPAN tarballs often contain more than one module.
• The tarball name does not necessarily reflect the name(s) of the module(s) therein.
• All tarballs are not *.tar.gz files; for instance, some are *.tar.bz2 files.
• The path to the *.pm file(s) is not necessarily found under a common, top-level lib directory.
• There may be multiple lib directories.
• The lib directories may contain files other than *.pm files.

For testing, I chose the following distributions:

libwww-perl-6.15

This was already mentioned. It contains multiple modules. The tarball name (libwww-perl-6.15.tar.gz) does not reflect the module names (all of which are in the LWP namespace). This does have a single, common, top-level lib directory containing only *.pm files. See its MANIFEST file for details.

Qt4-0.99.0

This was useful as it demonstrated all the points I made above: bzip tarball (Qt4-0.99.0.tar.bz2); multiple modules (which are neither called Qt4 nor in a Qt4 namespace); there's no common, top-level lib directory; there are multiple lib subdirectories which contain *.pm and other files. See its MANIFEST file for details.

Authen-SASL-Perl-NTLM-0.003

This was what you were using. It was mainly for comparison: it doesn't demonstrate any of the points I made above. See its MANIFEST file for details.

For additional testing, I made .tar.bz2, .tgz and .tar versions of libwww-perl-6.15 and .tar.gz, .tgz and .tar versions of Qt4-0.99.0.

Here's my test code:

#!/usr/bin/env perl

use 5.014;
use strict;
use warnings;

use Archive::Tar;
use List::Util qw{sum0};
use Test::More;

my @test_data = (
    {
        tarball_name_base => 'libwww-perl-6.15',
        filename_extensions => [qw{.tar.gz .tar.bz2 .tgz .tar}],
        expected_modules => [qw{
            LWP LWP::Authen::Basic LWP::Authen::Digest LWP::Authen::Nt
+lm
            LWP::ConnCache LWP::Debug LWP::DebugFile LWP::MemberMixin
            LWP::Protocol LWP::Protocol::GHTTP LWP::Protocol::cpan
            LWP::Protocol::data LWP::Protocol::file LWP::Protocol::ftp
            LWP::Protocol::gopher LWP::Protocol::http
            LWP::Protocol::loopback LWP::Protocol::mailto
            LWP::Protocol::nntp LWP::Protocol::nogo
            LWP::RobotUA LWP::Simple LWP::UserAgent
        }],
    },
    {
        tarball_name_base => 'Qt4-0.99.0',
        filename_extensions => [qw{.tar.bz2 .tar.gz .tgz .tar}],
        expected_modules => [qw{
            Phonon QImageBlitz Qsci Qt3Support4 QtCore4 QtCore4::class
+info
            QtCore4::debug QtCore4::isa QtCore4::signals QtCore4::slot
+s
            QtDBus4 QtDeclarative4 QtGui4 QtHelp4 QtMultimedia4 QtNetw
+ork4
            QtOpenGL4 QtScript4 QtSql4 QtSvg4 QtTest4 QtUiTools4 QtWeb
+Kit4
            QtXml4 QtXmlPatterns4 Qwt
        }],
    },
    {
        tarball_name_base => 'Authen-SASL-Perl-NTLM-0.003',
        filename_extensions => [qw{.tar.gz}],
        expected_modules => [qw{Authen::SASL::Perl::NTLM}],
    },
);

plan tests => sum0 map { scalar @{$_->{filename_extensions}} } @test_d
+ata;

my $map_re = qr{(?x: ^ .*? \b lib / ( [^.]+ ) )};
my $grep_re = qr{(?x: ^ .*? \b lib / [^.]+ [.] pm )};

for my $tarball_test (@test_data) {
    for my $filename_extension (@{$tarball_test->{filename_extensions}
+}) {
        my $tarball = $tarball_test->{tarball_name_base} . $filename_e
+xtension;

        my $tar = Archive::Tar::->new();

        $tar->read($tarball, '', {filter => qr{(?x: ^ [^/]* /? MANIFES
+T $ )}});

        my @manifest_lines = split /\R+/, $tar->get_content($tar->list
+_files());

        my @modules = map { (/$map_re/)[0] =~ s{/}{::}gr }
                        grep { /$grep_re/ } @manifest_lines;

        is("@{[sort @modules]}", 
            "@{[sort @{$tarball_test->{expected_modules}}]}",
            "Testing: $tarball");
    }
}
[download]

All of the expected_modules lists were taken directly from the distribution pages already linked to.

Here's the results:

1..9
ok 1 - Testing: libwww-perl-6.15.tar.gz
ok 2 - Testing: libwww-perl-6.15.tar.bz2
ok 3 - Testing: libwww-perl-6.15.tgz
ok 4 - Testing: libwww-perl-6.15.tar
ok 5 - Testing: Qt4-0.99.0.tar.bz2
ok 6 - Testing: Qt4-0.99.0.tar.gz
ok 7 - Testing: Qt4-0.99.0.tgz
ok 8 - Testing: Qt4-0.99.0.tar
ok 9 - Testing: Authen-SASL-Perl-NTLM-0.003.tar.gz
[download]