Regex 'or' operator avoid repetition

Question

How can I use the or operator while not allowing repetition? In other words the regex:

(word1|word2|word3)+

will match wo

Answer 1

You could use negative lookaheads:

^(?:word1(?!.*word1)|word2(?!.*word2)|word3(?!.*word3))+$

See it working online: rubular