combine isearch-forward-regexp and query-replace-regexp

[Hans-Christoph Wirth]

I usually fail to construct the correct regexp suitable for
query-replace-regexp at first attempt.  

isearch-forward-regexp does a nice job since it highlights all 
matching positions on the fly.

If I composed the right regexp with isearch-forward-regexp, how
can I supply it as an argument to query-replace-regexp?  M-p does
not help.

H-C