perlsyn to the rescue:

Fall-through

You can use the continue keyword to fall through from one case to the next:

    given($foo) {
    when (/x/) { say '$foo contains an x'; continue }
    when (/y/) { say '$foo contains a y' }
    default { say '$foo does not contain a y' }
    }
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Note: I'm looking in perlsyn from 5.012_002.