I'm not really saying that Perl should become a language you can write an OS in
Good, because anything you can write a half-decent operating system in is NOT a general purpose programming language. It would be far too low-level to be useful.
Perl, on the other hand, is definately general purpose. If you want evidence of this, look at the CPAN. Image/audio manipulation to web crawling to processing hundreds of file formats to cgi scripts to mod_perl to natural language processing and back again. If that isn't general purpose, what is?