# 'sort' COMPARISON FUNCTION FOR IP-ADDRESSES.
sub ip_compare {
   # GRAB THE TWO ARGUMENTS PASSED BY 'SORT'
   my ($a, $b) = @_;

   # SPLIT THE IP-ADDRESSES INTO FOUR =STRINGS= BY
   # THE PERIOD CHARACTER.
   my ($a1, $a2, $a3, $a4) = split('\.', @$a);
   my ($b1, $b2, $b3, $b4) = split('\.', @$b);

   # TYPECAST EACH COMPONENT AS INTEGERS, THEN
   # USE INTEGER '<=>' OPERATOR TO COMPARE NUMBERS.
   # USE A STACK OF SHORT-CIRCUIT '||' OPS WHICH WILL
   # STOP AT (AND RETURN) THE FIRST NON-ZERO RESULT
   # IN THE CHAIN.
   return 
      (int($a1) <=> int($b1))
   || (int($a2) <=> int($b2))
   || (int($a3) <=> int($b3))
   || (int($a4) <=> int($b4));
}