You do it the same way you did for the non-ref hash.

my (%H) = (1,100,2,200,3,300);
@A= @H{ (1,3) };

#BECOMES
my $H = { 1 => 100, 2 => 200, 3 => 300};
my @A = @{ $H }{1,3};
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So other than adding the curlys for the dereference it's the same.