My 5.18.2 on Linux dies the same way. B::Deparse shows this interpretation of your if statement:

if (grep((0 + $_ >= 99999999)), @times) {
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Note the parentheses. That is, you have a scalar comma expression with the grep and the @times array, which evaluates to @times. The grep is evaluating the expression 0 + $_ >= 9999999 on an empty list, but that's irrelevant.

Adding the parentheses properly works:

if (grep (((0 + $_) >= 99999999), @times)) { ...

# prints: Times: 1 2 3 4
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