I am looking for a powerful solution to run CSSless on httpd. I can't seem to find anything written in C. The best I've found so far was http://cpan.uwinnipeg.ca/dist/Apache2-Filter-CSS-LESS which I was even advised to not use because of CPAN.
CSSless is really amazing thing. A httpd module solution with caching available would be something tremendously useful.
If there is another way to install the module in question, please advice in the answer.
Are you meaning css.less? If so I'm not aware of any other dynamic server-side solution other than if used in node.js as described in the web page or the module you've just linked to, but the client-side processing option should do that you are looking for unless you are generating style dynamically (the styles and the code of less itself should be cached by the client browsers).
The main problem with using CPAN and similar and bypassing your Linux distribution's package management is that the module is likely to break next time your package manager updates related parts, so if you don't mind reinstalling then module and perhaps then cpan management scripts manually when they break you might be fine using that module, though I might be wary of a module that has not been updated for more then 18 months as it may not operate entirely correctly against later Apache updates (so I suggest testing it in a "throw-away" VM before trying it on any dev/test environment (and definitely before trying it on a live environment).