thekestrel,
Of course, there are the standards perlxs, perlxstut, perlguts^* and perlapi, but you can also buy Extending and Embedding Perl. It sounds to me like Inline::C is the way to go for your particular needs. I base that statement from the lack of requirements leading me to believe it wouldn't satisfy your needs. Having looked at both XS and Inline::C, it is easier to write and you can always modify the resulting XS if needed. * You might find PerlGuts Illustrated more useful.