open's prototype makes just passing @_ not work. See tilly's answer for the way to do this.

Update: well, I was so sure the above wouldn't work that I didn't even try it...so I wasn't misled by the apparent success. Because Tanktalus's code doesn't use warnings, he/she is missing this:

Ambiguous call resolved as CORE::open(), qualify as such or use &

So in fact the sub never even gets called. To call a sub with the same name as a builtin, you need to specify & (or have actually overriden the builtin as described in perlsub). Modifying the code to say &open(my $fh.... gives the error I was cautioning about:

Can't use string ("3") as a symbol ref while "strict refs" in use

due to the scalar prototype on open's first argument. (@_ == 3).