Hey, thanks for this project and if this feature doesn't meet the goals of it no hard feelings at all and feel free to close the PR :) - I just personally needed the feature and thought it might not be a bad idea to try to upstream if others also find it useful.

My motivation is that sometimes I need to benchmark a program (and specifically its cold start time) but the program doesn't terminate (think web servers) but just prints a text indicating that it's in a ready state.

For example a next.js app prints aReady in --- text when it's ready, so I use hyperfine with--until "Ready in" to get the elapsed time until the program prints that line in the output.

Let me know what you think :)

(p.s I can fix it on non-unix if there is interest in the feature, otherwise I don't need it for myself...)