Sometimes one has to peek under the hood or inside the black box .
How I fixed the surprisingly slow speed of the percentile function in Perl Data Language in #Perl (no C)
https://chrisarg.github.io/Killing-It-with-PERL/2025/11/30/Faster-quantie-calculations-in-PDL.html
Background :
https://en.wikipedia.org/wiki/Quantile