How do I modify the contents of a register without re-recording it?

Explanation

After recording a macro or yanking text into a named register, you may need to tweak it — fix a typo in a recorded macro, change a variable name in yanked text, or adjust a command sequence. Instead of re-recording from scratch, you can directly modify register contents using :let and Vim's string functions.

How it works

• @a accesses the contents of register a as a string
• substitute() works like :s/// but on a string value instead of buffer text
• :let @a = ... writes the result back into register a
• The 'g' flag replaces all occurrences, just like :s///g

Example

You recorded a macro in register q that changes foo to bar:

:echo @q
" Output: cwbar^[n

Now you need it to change foo to baz instead:

:let @q = substitute(@q, 'bar', 'baz', '')
:echo @q
" Output: cwbaz^[n

The macro is updated without re-recording.

Tips

• Use :echo @a to inspect register contents before editing
• You can also paste the register into a buffer with "ap, edit it, then yank it back with "ayy
• Other string functions work too: :let @a = toupper(@a) or :let @a = @a . 'extra text'
• To clear a register: :let @a = ''