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Perl, 73 bytes $_="A$/";$b=A;$a=$b++,s|^| |gm,s| (.*$a)(.*$/)|$&$1$b$a$2$&| until/Z/;say Explanation: # initialise output string and replacement character $_ = "A$/"; $b = A; #...

posted 6mo ago by jhnc‭ · edited 6mo ago by jhnc‭

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#2: Post edited by

jhnc‭ · 2026-03-24T07:14:52Z (6 months ago)

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~~# Perl, 74 bytes~~
$_="A$/";$b=A;$a=$b++,s|^| |gm,s| (.*$a)(.*$/)|$&$1$b$a$2$&|
while!/Z/;say
## Explanation:
```
# initialise output string and replacement character
$_ = "A$/";
$b = A;
# (
# set check character, update replacement character
$a = $b++,
# prepend a space to every line
s|^| |gm,
# find the line with check character
# - replicate before and after
# - adjust check -> check+replacement+check
# - fix up space count
s| (.*$a)(.*$/)|$&$1$b$a$2$&|
# )
# stop when string contains a Z
while !/Z/;
# display result
say
```
~~[Try it online!][TIO-mn48or7l]~~
~~[TIO-mn48or7l]: https://tio.run/##K0gtyjH9X1qcqpCWmlhSWpSqoF6cWKlu/V8l3lbJUUVfyVolydbRWiXRViVJW1unuCauRqEmPRfIUNDQ01JJ1ASR@po1KmoqhipJKokqRipqNVzlGZk5qYr6UfrWQMP@/wcA "Perl 5 – Try It Online"~~

# Perl, 73 bytes
$_="A$/";$b=A;$a=$b++,s|^| |gm,s| (.*$a)(.*$/)|$&$1$b$a$2$&|
until/Z/;say
## Explanation:
```
# initialise output string and replacement character
$_ = "A$/";
$b = A;
# (
# set check character, update replacement character
$a = $b++,
# prepend a space to every line
s|^| |gm,
# find the line with check character
# - replicate before and after
# - adjust check -> check+replacement+check
# - fix up space count
s| (.*$a)(.*$/)|$&$1$b$a$2$&|
# )
# stop when string contains a Z
until /Z/;
# display result
say
```
[Try it online!][TIO-mn4a2q8j]
[TIO-mn4a2q8j]: https://tio.run/##K0gtyjH9X1qcqpCWmlhSWpSqoF6cWKlu/V8l3lbJUUVfyVolydbRWiXRViVJW1unuCauRqEmPRfIUNDQ01JJ1ASR@po1KmoqhipJKokqRipqNVyleSWZOfpR@tZAs/7/BwA "Perl 5 – Try It Online"

#1: Initial revision by

jhnc‭ · 2026-03-24T06:40:02Z (6 months ago)

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# Perl, 74 bytes

<!-- language-all: lang-perl -->

    $_="A$/";$b=A;$a=$b++,s|^| |gm,s| (.*$a)(.*$/)|$&$1$b$a$2$&|
    while!/Z/;say


## Explanation:
```
# initialise output string and replacement character
$_ = "A$/";
$b = A;

# (

  # set check character, update replacement character
  $a = $b++,

  # prepend a space to every line 
  s|^| |gm,

  # find the line with check character
  # - replicate before and after
  # - adjust check -> check+replacement+check
  # - fix up space count
  s| (.*$a)(.*$/)|$&$1$b$a$2$&|

# )

# stop when string contains a Z
while !/Z/;

# display result
say
```

[Try it online!][TIO-mn48or7l]

[TIO-mn48or7l]: https://tio.run/##K0gtyjH9X1qcqpCWmlhSWpSqoF6cWKlu/V8l3lbJUUVfyVolydbRWiXRViVJW1unuCauRqEmPRfIUNDQ01JJ1ASR@po1KmoqhipJKokqRipqNVzlGZk5qYr6UfrWQMP@/wcA "Perl 5 – Try It Online"

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