inexact text search

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http://unix.stackexchange.com – Is there any utility like grep or even uniq but for inexact search or I should write it myself? I mean it will look at 90% (number may vary) matching, or smth like that. For example I have file with several strings: abc123 abd123 abc223 qwe938 In this case such utility should return the first three string or say they are similar. Of course I don't know any pattern of file's content like in case with grep or uniq. (HowTos)