There is explanation like this:

    my @@x;
    @@x <==  %hash.keys.grep: {/^\d+$/};
    @@x <== =<>;
    @@x <== 1..*;
    @@x <== gather { loop { take rand 100 } };

    @array{@@x}
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Shouldn't that be <<== rather than <== to be consistent with S06? As written, each line will overwrite the previous .todo, and @@x will contain an array of one list. E.g. from S06:

    0..*       ==>  @@foo;
    'a'..*     ==>> @@foo;
    pidigits() ==>> @@foo;

    for zip(@@foo) { .say }

        [0,'a',3]
        [1,'b',1]
        [2,'c',4]
        [3,'d',1]
        [4,'e',5]
        [5,'f',9]
        ...
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