Bug 162016

See https://rt.cpan.org/Ticket/Display.html?id=70232#txn-991950 for the
upstream report.

BSDPAN::ExtUtils::Packlist can be put into an infinite loop if write()
is given a packlist like "../.packlist".  This happens in the
ExtUtils-MakeMaker tests, specifically t/INSTALL_BASE.t, and was causing
hangs.

I have worked around this in MakeMaker's tests by having them set one
of the magic environment variables it recognizes to disable BSDPAN
registration.  It's a bit distressing that test modules were being
registered.  Perhaps BDSPAN should check that the module in question
is being installed into an official location before registering?  I
don't know how the BSDPAN stuff works.

Fix: 

get_dir_list() is the problem.  It's written in an unsafe fashion.
Instead of hacking off bits of the filepath with a regex and breaking
out of an infinite loop, it is safer and simpler to pull the filepath
apart into a list with File::Spec->splitpath and iterate through it.
How-To-Repeat: cd Some-CPAN-Module (ExtUtils-MakeMaker works)
perl Makefile.PL (to generate a Makefile)

Then run the following Perl program.

    use ExtUtils::Packlist;
    my $packlist = ExtUtils::Packlist->new;
    $packlist->{"Bar.pm"} = 1;
    $packlist->write("../.packlist");

It will enter an infinite loop.