Which programming language this site was programmed in?

Hello

I wanna to know which programming language this site was programmed in?

netcraft’s “what’s that site running” says –

Apache/1.3.33 (Debian GNU/Linux)
PHP/4.4.2-0.dotdeb.1
mod_perl/1.29

Apparently, “X-Powered-By: An infinite number of monkeys”.