Since both Node and Perl (and PHP as well, since you brought it up) are interpreted instead of compiled (there is lots of discussion about what this actually means, but for this discussion, we're talking about the same thing.), the only advantage you will see is based in the native optimizations in whatever is running the code.

Unless your code and/or data access/storage is horribly inefficient, any of the mentioned technology should be able to scale to a reasonable number of hits an hour with no trouble on reasonable hardware. In my experience, usually for larger applications, your slowdown starts with the data, not the code manipulating it. Every time you have to fetch data, you have to tickle the disk. Disks are the bottleneck for most every operation done on the machine under normal usage.

This whiffs of premature optimization. Unless you're planning something that's going to need to serve more than 10000 hits per hour (a number I've just pulled from my nethers, mind you) on launch, work in whatever you're comfortable with. By the time you start scaling past that, you'll have a better understanding of what you've done wrong with the first iteration and how to improve it. Remember, there are VERY large enterprise sites running on PHP and Perl, as well as Node. Wikipedia and Facebook run on PHP and have enormous user bases. Slashdot, Amazon, and Craigslist run on Perl. LinkedIn and Uber are on Node.

In short, unless you're in an exceptional circumstance where you're going to be launching to a global audience that will actually be funneling large volumes of traffic very shortly after launch, don't sweat it. Focus on maintainability. If you have to struggle to issue an update, or build a brittle stack because you're still ramping on the chosen tool, you're going to have more problems than how many hits you deliver.