I fail to see how not installing LWP will make your script more portable. Bundle LWP with your script when you distribute it if necessary. A reliance on things like 'lynx' is precisely what we're trying to avoid by using modules in the first place.

Your problem with your two system calls is probably because 'lynx' isn't in the script's path. Specify an absolute filename to the program or update your PATH accordingly.

If you "can't" install a module, you might just consider using IO::Socket and request the page by hand using Perl's native network support. That would be the "most" portable solution, but obviously you're never going to code yourself a solution that's as robust as using LWP in the first place will be.