http://www.perlmonks.org?node_id=69570

The specification is simple: given a list of numbers, return the two which are nearest to one-another. Assume that the list contains at least two numbers, and the return order is irrelevent. Some foolhardy attempts of my own follow:
# 114 chars sub nn1 { my@p;my$d;for(0..$#_-1){for my$n ($_+1..$#_){my$e=abs$_[$_]-$_[$n];i +f(!defined$d or$e<$d){$d=$e;@p=@_[$_,$n];}}}@p } # 100 chars sub nn2 { my@l=sort@_;$l[$_]=[@l[$_,$_+1]]for 0..$#l;pop@l;@{(sort{abs$$a[0]-$ +$a[1]<=>abs$$b[0]-$$b[1]}@l)[0]} } # 87 chars sub nn3 { @_=sort@_;my%d;$d{abs$_[$_]-$_[$_+1]}=[@_[$_,$_+1]]for 0..$#_-1;@{$d +{(sort keys%d)[0]}} }
Update: regarding the issue of duplicates, assume they are pairs like any other, so you would return duplicate numbers if they were present in the list.
   MeowChow                                   
               s aamecha.s a..a\u$&owag.print