open $fh, "<", $^X or die;
binmode $fh, ":raw";        # perldoc says: identical to 'binmode $fh'
print "3: ", join(' ', PerlIO::get_layers($fh, details => 1)), "\n";
close $fh;

open $fh, "<", $^X or die;
binmode $fh, ":raw:perlio"; # seems not useful (see below)
print "4: ", join(' ', PerlIO::get_layers($fh, details => 1)), "\n";
close $fh;