Oh, right, old code. CPAN is funny in that they have a central location to test multiple versions of code on multiple platforms and comment/patch them over time. I don't know of anything similar for any other language, probably because there isn't a CPAN equivalent for any other language (edit: there is JSAN and CCAN, but not quite the same).

http://stats.cpantesters.org/

Want to see how old code stacks up in testing? Let's pick a module and see all its dependencies and their test results. XML::Feed as a random example: http://deps.cpantesters.org/?module=XML%3A%3AFeed&perl=lates...

Hmm, says no results for some of them. Let's drill down and select HTTP::Negotiate to see its test results. http://www.cpantesters.org/distro/H/HTTP-Negotiate.html

Looks like the latest version has been tested on lots of platforms, and it's good! Let's pick a different piece of code, something older, say from 2005? https://metacpan.org/release/DOMIZIO/CGI-Builder-CgiAppAPI-1... http://www.cpantesters.org/distro/C/CGI-Builder-CgiAppAPI.ht...

Ah! So we see the last version it worked with and on which platforms, but on the latest perl it's failed its tests. We can drill down and see why the tests failed: http://www.cpantesters.org/cpan/report/c91a8b7c-4983-11e1-94...

Hmm, unprefixed autoloaded parameter. That's probably not too difficult to fix. I guess even though there's old crufty code that isn't always maintained across versions, we have pretty good visibility into when something failed, and with good tests we know why and how to fix it.

There's a lot more resources to take advantage of through CPAN, like bug trackers, review sites, development wikis, etc. http://en.wikipedia.org/wiki/CPAN