1. There are already modules out there that do all of that sort of processing (namely CGI), so all of that code is unnecessary.

2. Even if they wanted to re-invent that parsing stuff, they could have reduced their code to, like 10% by just pumping the name=value items into a hash instead of global variables.

With any CGI script, you almost always want to be sure your script works with taint-checking enabled. This prevents people from possibly passing specially crafted, unsafe arguments to your scripts where you don't expect it, with the intent of getting those strings injected into various system commands. Taint checking does a fairly good job identifying areas where this can happen. And the use of strict/warnings means that it's infinitely easier to track down bugs or problems with the code. A large script developed without strict or warnings probably has a few undiscovered/untickled bugs that would have been identified by now.