How do you use a macro to prepend text from a register to each line?
qaI<C-r>a<Esc>jq
Record a macro that inserts the contents of register a at the start of each line using a in insert mode, then moves down.
Tag: prepend
How do you use a macro to prepend line numbers to each line?
qaI1. <Esc>jq
Start at line 1, record a macro that inserts 1.