Given the combined list:
REGEX = .
REGEX = (.)
REGEX = .*
REGEX = .*?
REGEX = ^.
I'd expect that 1, and 5 will be very similar, and the best choices. 2 requires the regex engine to create a capture group, which you don't appear to need. 3, depending on the efficiency of the regex engine, may decide to consider all the characters in the event. 4 should reduce to 1, but the regex engine will have to take that extra step.
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