Taint mode does not help against null bytes (or any other bytes) in your read_file "$page.html" example. Reads are not checked for tainted data. Writes are though, so write_file "$page.html" would've been stopped by the -T switch.

In short, I'd like to add this: Don't think -T will do the job for you! Just think it may help you if you slipped up.

ihb