Hmm, WWW::Selenium and the associated SeleniumRC 1.0 stuff has been deprecated for a few years now, in favor of Selenium Webdriver 2.X (and even 3.0 - there are Selenium Webdriver 3.0 betas out now). Unfortunately, I have no idea how to accomplish this with Selenium RC - perhaps this set_timeout method is what you’re looking for? I’m not really sure…
FWIW, with Selenium::Remote::Driver and using Webdriver, you’d use S::R::D's set_timeout with the timeout name of page load as discussed in the POD for that method and set it to an appropriate value. Afterwards, I think attempting to load a page that exceeds the custom timeout will throw an exception that S::R::D with turn into a die that you’ll probably want to catch and handle appropriately.
I’d assume it’s generally similar in SeleniumRC (manage a timeout value with a different subroutine, then call the subroutine for loading a page), but again I don’t have any experience with RC anymore and no idea if my assumption actually holds water.
Good luck!