Yes, ^ can be used to negate a character class as well as anchor a match - it was not the parens that changed context, it was the square brackets (which denote a character class). Check out the docs, in particular, the sentence below xdigit.

jeffa

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)