Just for fun:

use strict;
use warnings;

my $raw = join '-', 1 .. 30;
my @ranges = ([5, 10], [14, 18], [22, 27]);

$raw =~ s/(\d+)/(grep {$1 >= $_->[0] && $1 <= $_->[1]} @ranges) ? 'X' 
+: $1/eg;

my @parts = split /((?:-X)+-)/, $raw;
my $sub = 'A';

for my $part (@parts) {
    next if $part =~ /X/;
    $part =~ s/\d+/$sub/g;
    $sub = 'A' if ++$sub eq 'C';
}

print join('', @parts), "\n";
[download]

Prints:

A-A-A-A-X-X-X-X-X-X-B-B-B-X-X-X-X-X-A-A-A-X-X-X-X-X-X-B-B-B
[download]