How about a little DIY?

This is untested, but...

use POSIX qw(floor);

sub dec2Bin($) {
  $n = shift;
  while ($n != 0) {
    $k = $n % 2;   
    $n = floor($n / 2);
    $b = $k . $b;
  }
  print "$b";
}
[download]

chiller