How to access the last expression used in search in Vim?

Question

When doing more complicated search & replace operation in Vim I often try it out in search and only if it finds what I expect I use search & replace.

Is there a way how to access the last value from search and put it into search & replace or alternatively, to put this last value into a register?

Answer 1

From the VIM wiki page:

:%s//<c-r>//g
    Replace each match of the last search pattern with the / register (the last search pattern). 
    After pressing Ctrl-R then / to insert the last search pattern (and before pressing Enter to perform the command), you could edit the text to make any required change. 

Answer 2

If you don't need to edit the search regex you can omit it and vim will use the last search for the pattern.

:%s//<replacement>/

---

From :h :s | /If the {pattern}

If the {pattern} for the substitute command is empty, the command uses the
pattern from the last substitute or `:global` command.  If there is none, but
there is a previous search pattern, that one is used.  With the [r] flag, the
command uses the pattern from the last substitute, `:global`, or search
command.