You need to tell us more. Do you mean something like (pseudo-code follows)

my @char = split(//,$word);

my $value = 0;
my $place = 0;
foreach revers(@char){
     $value += ord($_) * 256 ** $place;
     $place++;
}
$value = $value % (256**2);
[download]

Clearly, there could be some problems here if the word is longer than 4 characters.

Or you could try pack and unpack and, of course, Super Search.