I just tried it out in bash, it works pretty much the same way it does in the gif. This description of the functionality in the readme is succinct: percol - r

I just tried it out in bash, it works pretty much the same way it does in the gif. This description of the functionality in the readme is succinct: percol - receives input lines from stdin or a file, - lists up the input lines, - waits for your input that filter/select the line(s), - and finally outputs the selected line(s) to stdout.