Interactive search/replace regex in Vim?

Question

I know the regex for doing a global replace,

     %s/old/new/g

How do you go about doing an interactive search-replace in Vim?

Answer 1

If you just want to count the number of occurrences of 'abc' then you can do %s/abc//gn. This doesn't replace anything but just reports the number of occurrences of 'abc'.