As poj says. Heh... didn't know that there's a module for that. This is what I have in my toolbox

my %hash;
my @chars     = (0..9,'A'..'Z','a'..'z',map{chr$_}32..47,58..64,91..96
+);
@hash{@chars} = 0..$#chars;

sub encode_base {
    my ($base,$num) = @_;
    my ($rem,@ret);
    while ($num) {
        push @ret, $chars[($rem = $num % $base)];
        $num -= $rem;
        $num /= $base;
    }
    return join '', reverse @ret;
}

sub decode_base {
    my ($base, $str) = @_;
    my $num;
    $num = $num * $base + $hash{$_} for $str =~ /./g;
    $num;
}
[download]

which is basically the same, but lets you encode/decode with a base up to 91. So,

my $number = decode_base 36, 1009;
say lc encode_base 36, $number++ for 0..36;
[download]

does what you want. Also, these subs can be used to convert from decimal to binary, octal, hex and reverse, using 2, 8 and 16 as base. But I'd use the perl builtins for that ;-)