As Tortue points out, all the ones using lexigraphic sorting fail on some sets of numbers. Stripping leading spaces and newlines, my stab weighs in at 87 characters: 

sub nn {
    @_=sort{$a<=>$b}@_;
    $_[1]-$_[0]>$_[$_+1]-$_[$_]and@_[0,1]=@_[$_,$_+1]for 1..@_-2;
    @_[0,1]
}

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

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