<C-r>/ inserts a special register
"/ (the last search string) at the actual position in the command line. Type
:register and you'll see all registers with their content. There is no register for the subtitute-text.
Register are AFAIK the only way to keep such informations.
You could write a vim function, that extracts the replacement part of the substition command stored in register
": with a regular expression. You could bind that function to a key. But that only works as long as you do not enter another command, which would overwrite the
Another idea: You have to type foo, bar and baz at least once, you could instead search for them in the text, highlight them with
v and yank them into a separate register:
Now you can use the registers as long as you want (as you don't overwrite them).