Just as memory hungry, still not order preserving, and still broken with regards to undefined values, but faster approach: 
my %seen;
@seen{@list}=();
my @uniq = keys %seen;

[download]
And if you want to wrap it up without "leaking" lexicals: 
my @uniq = do {
    my %seen;
    @seen{@list}=();
    keys %seen;
};

[download]
This approach does not (explicitly) iterate - more of the data structure setup work is done implicitly by perl.

Makeshifts last the longest.

In reply to Re: Perl Idioms Explained - keys %{{map{$_=>1}@list}} by Aristotle
in thread Perl Idioms Explained - keys %{{map{$_=>1}@list}} by broquaint

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