Revision 01c5cfed-dae2-4e1b-a090-7b055810cac4 - Code Golf Stack Exchange
# [V], <s>28, 26, 25</s>, 23 bytes ([Competing](https://codegolf.meta.stackexchange.com/q/12877/31716))
<pre><code>¬A[/a
lDÓ./& ò
ò-Ûä$Û>
</code></pre>
[Try it online!][TIO-j6p7fw2g]
[V]: https://github.com/DJMcMayhem/V
[TIO-j6p7fw2g]: https://tio.run/##ASUA2v92///CrEFbLxJhCmxEw5MuLyYgw7IKw7Itw5vDpCTDmz7///9G "V – Try It Online"
Note that although I have been planning on adding [certain features](https://github.com/DJMcMayhem/V/commit/5de2c51e581014a2693a8c6d68cdfb3378343510) for a long time, this challenge was what convinced me to finally do it.
The output contains one leading space on each line and one trailing newline.
Hexdump:
00000000: ac41 5b2f 1261 0a6c 44d3 2e2f 2620 f20a .A[/.a.lD../& ..
00000010: f22d dbe4 24db 3e .-..$.>
Explanation:
¬A[ " Insert 'ABCDEFGHIJKLMNOPQRSTUVWXYZ['
/ " Search for...
<C-r>a " The input
l " Move one character to the right
D " And delete every character after the cursor
Ó " Search for...
. " Any character
/ " And replace it with...
& ò " That character followed by a space and a newline
ò " Recursively...
- " Move to the beginning of the next line up
Ûä$ " Make *line number* copies of the current line
Û> " And indent this line by *line number* spaces