Did you perhaps mean (...)[-1]?

That's a list slice. The expression in the parens is evaluated in list context. The expression in the square brackets must return a list of indexes. The slice returns the elements of the returned list identified by the indexes. Negative indexes are relative to the end of the list, where -1 is the last element of the list.

( grep { $_ % 4 == 0 } 1..10 ) )[-1]   # The last num divisible by 4.
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