4.4BSD/usr/src/contrib/perl-4.036/atarist/test/printenv

$exit = 0;
$\ = "\n";
if($#ARGV >= 0) {
    foreach (@ARGV) {
	if(defined $ENV{$_}) {
	    print $ENV{$_};
        } else {
	    $exit = 1;
        }
    }
} else {
    foreach (sort keys %ENV) {
	print $_, '=', $ENV{$_};
    }
}
exit $exit;