How do I use yanked text as the replacement in a substitute command?

Explanation

The \=@0 replacement expression inserts the contents of register 0 (last yank) as the replacement text. This lets you yank some text, then use it in a substitute command without retyping it.

How it works

1. Yank the replacement text: yiw (or any yank command)
2. Search and replace using the yanked text:

:%s/old_pattern/\=@0/g

Vim evaluates @0 as the contents of the yank register and uses it as the replacement.

Step-by-step example

" 1. Yank the word 'newFunction'
yiw

" 2. Replace all occurrences of 'oldFunction' with the yanked text
:%s/oldFunction/\=@0/g

Using other registers

" Use named register a
:%s/pattern/\=@a/g

" Use system clipboard
:%s/pattern/\=@+/g

" Use last search pattern as the search part (empty pattern)
:%s//\=@0/g

The ultimate yank-and-replace workflow

" 1. Yank replacement text
yiw

" 2. Search for the target (sets the search register)
*

" 3. Replace all with empty pattern (reuses *) and register 0
:%s//\=@0/g

Tips

• \=@0 is more reliable than trying to paste text with special characters into the replacement string
• This handles newlines, slashes, and backslashes correctly — no escaping needed
• @" is the unnamed register, @0 is the yank register, @+ is the clipboard
• You can also use <C-r>0 in the command line to paste the register literally (but special chars may need escaping)
• Documented under :help sub-replace-expression and :help expr-register