One example is recording a macro - you can then execute it an arbitrary number of times. I've used it e.g. to add quotes and commas to a list of data so it's a proper string array, or to change a string into an object where a property is the former simple string. The workflow would be - record the abstracted process using vi editing commands, then play the macro over where needed.

Probably best to see it in action to fully appreciate it.