Calculate codon number

codon_number.pl

sub codon_sequence {
    my ($self, $n) = @_;
    my ( $r, @s );
    for my $i ( 0 .. 2 ) {
        $r = $n % 4;
        $n = $n >> 2;
        unshift( @s, $nucleotides[$r] );
    }
    return join( '', @s );
}