use strict;
use warnings;
my @strings = ('abzdefghijk',
'a b z d e f g h i j k',
'',
'abzde          fghijk',);

print $_, " => ", hc($_), "\n" for @strings;

sub hc {
    my $string = shift;
    my $erg = 0;
    my $max = int(length($string) - 1);
    # this line is your algorithm!
    $erg += (ord(substr($string,$_,1)))*31**($max-$_) for 0..$max;
    $erg;
}