Rule 1, which you mention, provides the answer—except that maybe you have the wrong idea of what the ‘hash name’ is. Namely:

@hash{ qw/key1 key2 key3/ }
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is the slice of the hash named 'hash' (not '%hash') corresponding to the indicated keys. If you want to slice a referent, just stick the (suitably bracketed) reference in place of the name:

@{ $hashref }{ qw/key1 key2 key3/ }
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(as AnomalousMonk pointed out below).