I think I had \1 and \2 backward. Then you just have to disallow the trivial solution: 

$s = 'aaaabaaaabaaaaabaaaab';
$s =~ /^((.*?).*?)(?=.)\1*\2$/ and print "$2/$1";

[download]

(Update: Dropped the unneeded () around \1 that I had introduced while debugging. You probably also need to change .*? to .* so you get the longest solution not the shortest.)

- tye        

In reply to Re^5: Finding repeat sequences. (only regex!) by tye
in thread Finding repeat sequences. by BrowserUk

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