It's been easier for me to use "Net::Netmask".

  use Net::Netmask;

  $range = undef;
  $range = "$ip/$maskip";
  print "-- RANGE: \"$range\"\n";
  $msess = undef;
  $msess = new Net::Netmask($range); 

  $table = undef;
  $msess->storeNetblock($table);
  $wireip = undef;
  $wireip = $msess->base();
  $bcastip = undef;
  $bcastip = $msess->broadcast();
 
  if($debug == 1)
    {
    print "WIREIP: \"$wireip\"\n";
    print "MASKIP: \"$maskip\"\n";
    }

   # Dump all ips in range
   $oip = undef; 
    foreach $oip ($msess->enumerate(0))
      { 
      print "OIP: \"$oip\"\n"; 

      }
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This has helped with finding ip's in subnets.. Especially When 1000's of subnets are used with different masks.