XSLT: Finding last occurence in a string

Question

Given a form number like:

ABC_12345_Q-10

I want to end up with:

ABC12345

So I need to find the position o

Answer 1

Generalized one -

substring($string,1, string-length($string)-string-length(str:split($string, '_')[count(str:split($string, '_'))]))

Idea is to get the index of last occurrence by splitting string.

Index of last occurrence = string-length($string) - length of last string after split