abitlity to know a caracter position an do a substr

Hello,

First many thanks for this great soft (I use it since many years now)

It would be useful if we can do a sustr passing a string position in parameter

example

for the file

official-decision-multiple-urbanplan24.pdf

you do

%b(1,"-multi")

gives :
official-decision.pdf

Ideally you should keep p as the third parameter to know if we start from the beginning or the end of the string.
Adding a fourth parameter indicating which occurrence of the searched string (first, second, x) should be used for substr would be a real improvment.