I'd guess that pulling that try-catch out of the loop would make things go much faster. Nim doesn't use 0-overhead exceptions, so setjmp needs to be called each

I'd guess that pulling that try-catch out of the loop would make things go much faster. Nim doesn't use 0-overhead exceptions, so setjmp needs to be called each time the try-catch is entered. You should also use the re module, PEGs is not nearly as optimized as PCRE.