sub key {
    $kp= shift;
    $caesar= shift;
#version 1 - this works, the starting point
#     foreach (split(//, $kp),'a'..'z') {
#         if (not exists $p2C{$_}) {
#             $p2C{$_}=chr(ord('A')+(($a++)+$caesar)%26);
#         }
#     }

#version 2 - this doesn't work - because autoincrement $a++ gets off when the key already exists!
    foreach  (split(//, $kp),'a'..'z') {
        $p2C{( exists $p2C{$_} ? '#' : $_)} = chr(ord('A')+(($a++)+$caesar)%26);
    }

    %C2p = map {$p2C{$_} => $_} (keys %p2C);
    $p2C{' '}=' ';
    $C2p{' '}=' ';
}    

sub printKeys {
    my $href = shift;
    print "\nCT: ";
    print(($_).' ') foreach (sort keys %{$href});
    print "\npt: ";
    print(($$href{$_}).' ') foreach (sort keys %{$href});
    print "\n";
}

key ('thequickbrownfoxjumpsoverthelazydogs',10);

printKeys(\%p2C);
printKeys(\%C2p);