#!/usr/bin/perl

my $string = '-13-4-1-2-3-13-1-2-13-1';
my $search = '-13-1';

while($string =~ m/$search/g){
   my $substr = substr $string, 0, $+[0]- length $search +1;
   $substr =~ tr/-//d;
   print length $substr;
}