This might be faster: 

^
(.)
(?: (?: \1                     ) (*COMMIT) (*FAIL) | (.) )
(?: (?: \1 | \2                ) (*COMMIT) (*FAIL) | (.) )
(?: (?: \1 | \2 | \3           ) (*COMMIT) (*FAIL) | (.) )
(?: (?: \1 | \2 | \3 | \4      ) (*COMMIT) (*FAIL) | (.) )
(?: (?: \1 | \2 | \3 | \4 | \5 ) (*COMMIT) (*FAIL) | (.) )
\1
\z

[download]

In reply to Re^2: Nonrepeating characters in an RE by ikegami
in thread Nonrepeating characters in an RE by BernieC

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