Getting the indexes of duplicate elements in arrays (Ruby)

I have an array in Ruby that has some duplicate elements. E.g.:

fruits = ["apples", "bananas", "apples", "grapes", "apples"]

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fruits.to_enum.with_index.select{|e, _| e == "apples"}.map(&:last)

fruits.each_index.select { |i| fruits[i]=="apples" }

fruits.each_with_index.select{|v, i| v == "apples"}.map(&:last)