The composite (or prime) filter regexp is brilliant. $^(11+)(\1)+$ see OPs linke...

		agumonkey on July 29, 2014 \| parent \| context \| favorite \| on: Sculpting text with regex, grep, sed, awk, emacs a... The composite (or prime) filter regexp is brilliant. $^(11+)(\1)+$ see OPs linked article http://zmievski.org/2010/08/the-prime-that-wasnt for details