You can still use the two base calculations in this shader, but you will need a separate switch for each colour channel. That's easy enough to implement in nodes, but sorry I haven't learnt Matmatic yet. (I don't agree that non-familiarity with Matmatic syntax should exclude anyone from taking part in this discussion).

The equation implemented in this shader is:
IF(x <= .0031308, 12.92 * x, 1.055 * (x ** (1/2.4)) - .055).

Maybe the subject of sRGB correction would benefit from a new thread? RV is dealing with GC at present. Just a suggestion...  :O)

(edit) oh, I didn't see bb's post. Is it not possible that one colour channel could require the linear part of the graph, but another could require the non-linear part? So wouldn't we need to switch them separately?

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)