I'm new to perl, yet an old dog with other languages. I'm looking for a way to scan through a very long list of 64-bit integers and find all pairs in the list that share only the least significant bit being set (($num1 & $num2)==1). The code below takes much too long.

# find all integers in the list that do not share any bits except the 
+lsb.

my %MatchedIntegers=(); #my output
foreach my $i1 (@LongListOfIntegers)
{
  foreach (@LongListOfIntegers)
  { #if a match (only least significant bit overlaps),
    #  add to hash of hash, I don't care about the value.
    $MatchedIntegers{$i1}{$_}=() if (($i1 & $_) == 1) ;
  }
}
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Any ideas? It seems that this should be a very fast thing to do. For a list of ~4,000 values, it takes 2 seconds. I want to keep the code in perl (not link to C/C++). I need the output in a hash table, but it could be a hash of arrays instead of a hash of hashes. Thanks,