Xah Lee has a very useful post on the repeat complex command command. A complex command is one that uses the minibuffer. That’s different from the repeat command that is usually bound to 【Ctrl+x z】.
What happens is that the Elisp for the command is placed in the minibuffer and you can edit it before repeating the command. That’s nice if, say, you made a mistake on a regexp and want to fix it and retry the command. Oddly, I knew about only the repeat command but not the repeat-complex-command version so I’m was glad to see Lee’s post. Take a look at his post for the details.
The repeat-complex-command command is bound to a terrible key sequence so if you find yourself using it a lot you’ll probably want to rebind it to something convenient.