Spaces are not permitted in escape sequences. That includes \x20, \c[ and \ub.

\b, if considered an escape sequence, is the escape sequence in its entirety. It can be preceded and followed by anything.

In reply to Re: Regex bug? (/u not cooperating with /x) by ikegami
in thread Regex bug? (/u not cooperating with /x) by mrpeabody

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