Yes. See http://search.cpan.org/~drolsky/Catalyst-Request-REST-ForBrowsers-0.03/lib/Catalyst/Request/REST/ForBrowsers.pm#$request->looks_like_browser() for the rules in the hueristic. Basically, there's a tension between e.g. the expectation that PUTting a new resource returns 201 on the one hand and the fact that browsers don't really handle that well on the other, and this is a good compromise.