I used to work in a Perl shop and must admit that the language is very simple for tasks like these, but as you mentioned it's not fast at execution time. I'm now a Go programmer professionally but I taught myself the language while in college purely out of interest and eventually found my way to the job, not the other way around. I've recently been learning a little rust because of how much that language comes up in conversations around Go. I find the concept of the borrow checker nice but I have to admit I feel lost like I am in most flavors of new fancy framework js. That's not to say Rust is really anything like js, but the learning appears the same to me as someone who's convinced they could learn just about any programming language if it was necessary (over time I've seen procedural, OOP, declarative and functional stuff but never programming logic outside of the prolog code I wrote in school).

Go isn't made for your specific task at hand but it's a very easy language to pick up and it has good directory traversal standard library code and good regex (even though with time perl's has been optimized to be faster and I think it's written in C++) but more than anything Go is "cloud native" programming in that an awful lot of new microservice tech stacks are centered around it, docker and kubernetes are written in it, and there's a thriving community whose focus is generally web-first and performance-oriented. This means for your use case there might already be a large cohort of gophers that have asked the stackoverflow questions for you

I personally would push you towards the NYT Profiler for Perl before I would towards Rest, but that's because I know you wouldn't waste any time being able to get to the task at hand and then make it go faster, and I expect all but a few rustaceans would be able to do so with the same speed.

Whatever you pick I wish you the very best of luck!