backtracking inside the negative lookahead

Question

I want to find how the backtracking works inside the negative lookahead. like in ...

     ^(?!.*some My Words$).*$

how far the the regex engine will try the first .*. I am testing somewhere awesome My Words. Which I expect should be rejected, but not. So how the backtracking is working here and how this is happening?

Answer 1

The sample example would be rejected for the above regex.

.* eats everything and reaches to the end. i.e after last s.Then it backtracks 1 by 1 till it matches some My Words.

With .*? it would match till the first some My Words

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.*? is better than .* but performance gain would be significant only for large strings