It is, indeed, very much a subjective question. I can totally conceive that in 2010, Perl or PHP (and even Python or Ruby) could equally serve you for such a project. The difference is not going to come from the language itself as much as the tools, best practices and community.
Among these languages, I am most familiar with Perl, so let me try to offer an answer from that perspective, regarding your needs.
Text and XML parsing: Perl has very robust support for text parsing of even very long files (as long as you don't slurp), and allows powerful, clear and easy regex programming. It has clear built-in Unicode support and standard trans-encoding tools (the Encode module), which is very handy when it comes to user interfaces. It also has a direct binding for libxml2 in the form of a standard, fast and well-maintained module: XML::LibXML.
Relational DB Support: In addition to the standard database interface (DBI) which allows direct SQL queries to a number of DBMSes, there are a number of frameworks to make DB-to-Webdoc management easier while still powerful. The most famous probably being Catalyst.
HTML Document presentation: Mason is my favorite web application delivery engine. The integration with Perl is so elegant, yet it does not sacrifice templating patterns or language features.
Heavy load handling: There are as many solutions as there are load problems to solve. Perl offers bindings for memcached: Cache::Memcached (written in Perl) and Cache::Memcached::Fast (written in C).
Balance that out with your personal preferences regarding syntax and general language philosophy, and you could very much join the Enlightened Perl community quite soon :)