Bug #53236 for File-Spec: File::Spec should NOT cache $ENV{TMPDIR}

File::Spec caches $ENV{TMPDIR}; see this code in File/Spec/Unix.pm:

sub tmpdir {
    return $tmpdir if defined $tmpdir;
    $tmpdir = $_[0]->_tmpdir( $ENV{TMPDIR}, "/tmp" );
}

This prevents you from being able to change $ENV{TMPDIR} on the fly.  Arguably, you shouldn't do that
because you should just invoke File::Temp (which calls File::Spec) with a proper directory argument, but
often you use Perl modules that internally call File::Temp and over which you have no control.  It is therefore
desirable not to cache $ENV{TMPDIR}, but to reread it out of the environment every time.

Regards,

David.