# `\L`, `\U`, `\E` for fractals in GNU sed The case switching special sequences help in "toggling" a line. An example is the following challenge to produce a fractal X on [anagol](http://golf.shinh.org/p.rb?Fractal+X), whose shortest sed solution by mitchs et al is reproduced here. ``` s/^/X\n/ : s/^.\{,27\}\n/&\L&\U&/mg //s/[ X]/& &/g s/x/ X /g t ``` [Try it online!](https://tio.run/##K05N@f@/WD9OPyImT5/LigvI1Iup1jEyj6kFCqjF@KjFhKrp56Zz6esX60crRMTqqymo6acD1VXoK0QoAFkl//8DAA "sed 4.2.2 – Try It Online") If the fractal uses another character to fill it, then at the end you can add a transliterate.