Quoting Anthony (anthony-luv@hogan.id.au):
Australian domain whois also doesn't show expiry info.
Quite. This astonishing-to-me-in-2007 fact is highlighted prominently in my referenced _Linux Gazette_ article. The domain I tested, as revealed in the article, was, in fact, luv.asn.au. (That revelation means that all three implementations of the checking script are useless for .au domains, sadly. Fortunately, even for hosts in Oz, .au is not the only possible TLD. For hosts where that DNS constraint applies, true, other solutions would be required.)
Unfortunately you can't poll whois for a .au domain more than 20 times a day from the same IP.
FWIW, Ben Okopnik's (and, IIRC, Jesse Monroy's) Perl code includes rate-limiting code for some _other_ TLDs that are punitive of frequent queries, albeit not quite that punitive.