While this may not have many new ideas, it does weigh in at 117 characters and deal with dups:
sub nn2 {
    my$s=sub{sort{$a<=>$b}keys%_};
    @_{@_}=0;@_=&$s;%_=();
    $_{abs($_[$_]-$_[$_+1])}=[@_[$_,$_+1]]for 0..$#_;
    @{$_{(&$s)[0]}}
}

[download]

Neat problem!

In reply to Re: (Golf) Nearest Neighbors by satchboost
in thread (Golf) Nearest Neighbors by MeowChow

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