Anything in capturing (plain) parentheses will be returned as a separate item in the split results. If you need parentheses for grouping, use non-capturing parentheses, which open with (?: instead of just (.

No matter how many alternative separators you have, you don't need parentheses at all unless the alternatives are only part of the separator and you need to "factor out" common substrings. For example, if your valid separators were "foo&&", "foo||", and "++", you could split on

/foo(?:&&|\|\|)|++/
[download]