The question is not fair.

In any language, unless you are programming in the kernel, you will require the mmap system call in order to access memory mapped hardware. By restricting to what's described in the perlfunc and perlop manpage, you are forbidding use of mmap.

So notwithstanding your restriction, it's actually just as easy to do in Perl as in C: In C, use mmap(), in Perl use Sys::Mmap.