$file //= default_file();
my $self;
if (ref($file) eq 'SCALAR') { # used by some tests
open my $fh, '<', $file or die; # PerlIO::scalar
$self = config_fh_parse($fh, "\n", '=');
$file //= default_file();
my $self;
if (ref($file) eq 'SCALAR') { # used by some tests
open my $fh, '<', $file or die; # PerlIO::scalar
$self = config_fh_parse($fh, "\n", '=');