Assuming every value of %uni_refs is a unique index of @allrefs (which I judge to be quite likely), the following is a solution that scales better (O(N) instead of O(N log N)). 

my %keep = map { $_ => 1 } values %uni_refs;

my @refs = @allrefs[ grep $keep{$_}, 0..$#allrefs ];

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In reply to Re: Code Interpretation by ikegami
in thread Code Interpretation by Perl_Ally

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