A lot of comments have been made regarding the usefullness finding repeating sequences. Without making any comments for or against, I'd just like to point out that as several recent nodes have pointed out, a very simple way to find commonalities between strings (or even within a single string) is to use compression, and analyze the size ratio between the compressed/raw versions.

for example...

laptop:~> perl -MCompress::LZW -lne 'print " -> ", compress($_), " / $
+_ == ", length(compress($_))/length($_);'
a
 -> a / a == 2
aaa
 -> a / aaa == 1.33333333333333
aaaaaaaaaaaaaa
 -> a / aaaaaaaaaaaaaa == 0.714285714285714
qwre1qwre2qwer3
 -> qwre12er3 / qwre1qwre2qwer3 == 1.6
qwertgfdsazxcv
 -> qwertgfdsazxcv / qwertgfdsazxcv == 2
^D
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