Math operations in regex

Question

I need to add a number to a backreference while doing a replace operation.

e.g. I am rewriting a URL

www.site.com/doc.asp?doc=321&language=1
         


        

Answer 1

using Perl:

s/.*doc=(\d+).*/"www.site.com\/headline\/".($1+100000).".article"/e;

as you've done with e flag, the right part becomes now an expression. so you have to wrap the non-capture part as strings.