I got bored, and tried to write my own base converter (without having first checked CPAN where I would have found Math::BaseCalc which would do what you want just fine, I think). It runs into problems with large numbers (The md5 value listed in your post, for example).

But if anyone's interested in tinkering, I'll post what I came up with... I think I could fix it by using Math::BigInt, but haven't tried just yet.

sub convert_base
{
   my($input_string,$from_base,$to_base) = @_;
   my($working_number,$current_digit,$i);
   my($quotient,converted_number);

   #
   # Convert input string to dec.
   #
   for ( $i = 0; $i < length($input_string); $i++ )
   {
      $current_digit = uc(substr($input_string,$i,1));

      if ( $current_digit !~ m/[0-9]/ )
      {
         $current_digit = ord($current_digit) - ord("A") + 10;
      }

      $working_number += $current_digit *
                         ($from_base ** (length($input_string) 
                                         - $i - 1));
   }

   # Figure out dec value of this digit.

   #
   # Convert int to new base.
   #
   while ( $quotient = int($working_number / $to_base) )
   {
      $current_digit = $working_number % $to_base;
      if ( $current_digit > 9 )
      {
         $current_digit = chr($current_digit - 10 + ord("A"));
      }

      $converted_number = $current_digit . $converted_number;

      $working_number = $quotient;
   }

   #
   # We've dropped out because there's only a bit of remainder left.
   #
   $current_digit = $working_number;

   if ( $current_digit > 9 )
   {
      $current_digit = chr($current_digit - 10 + ord("A"));
   }

   $converted_number = $current_digit . $converted_number;

   return $converted_number;
}
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