Replace string with another string at same indentation level

vim-regex.md

Input

                  =r.text_field :first_name
                .control-group
                  =r.label :middle_name, "Middle Name", class: "control-label"

Output

                  .controls
                    =r.text_field :first_name
                .control-group
                  =r.label :middle_name, "Middle Name", class: "control-label"

VIM regex

:%s/\(^\s\+\)\(.*_field.*\)/\1\.controls\r\1 \2/g

Note: parenthesis in search regex have to be backwhacked in vim ( becomes \(.

• :%s/ this starts the search command :P
• \(^\s\+\) this finds the whitespace at the beginning of each line
• \(.*_field.*\) this finds strings that have "_field" in them
• \1\.controls\r\1 \2 the replace command with backreferences FTW