use strict;

my %p2C;
my %C2p;
key ('thequickbrownfoxjumpsoverthelazydogs',10);
printKeys(\%p2C);
printKeys(\%C2p);

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

sub key {
    my @kp = grep /[a-z]/, split //, shift;
    my $caesar= shift;
    my @alpha = ('A'..'Z');
    push @alpha, shift @alpha for (1..$caesar);
    foreach (@kp,'a'..'z') {
        if (not exists $p2C{$_}) {
            my $k = shift @alpha;
            $p2C{$_}=$k;
            $C2p{$k}=$_;
        }
    }
}