I'm sure that's the cause. Their test script is just a straight `echo` of the input, so each test process will exit essentially immediately - it's unlikely the

I'm sure that's the cause. Their test script is just a straight `echo` of the input, so each test process will exit essentially immediately - it's unlikely the parallel aspect actually kicks in to any decent degree. The majority of the test is spent in the Rust/Perl code vs actually running commands. That said, while the test isn't hugely useful, the fact that this Rust implementation has much less overhead is still a notable improvement. To add to this, parallel mentions as much in its man pages (that there is a certain startup cost, and a certain job-startup cost), and offers tips for speeding up the processing of jobs which exit fairly fast. But there's no reason you couldn't also do those things in the Rust version, so it's going to win every time. When dealing with commands which take a while to complete though, the extra overhead of the perl script would probably be negligible.