Regex Editor & Tester

Matches an empty string or an odd-length sequence (1, 3, 5, ... characters) consisting only of a, b, or c where no character is immediately preceded by itself, e.g. 'a', 'aba', or 'abcba' but not 'aa' or 'ab'. Each character uses a negative lookbehind to forbid consecutive repeats, and the nested ((X X)*)? structure enforces odd counts. Useful for validating or tokenizing alternating sequences over a limited alphabet.