#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11147549
use warnings;

my $ranges = '5-10,14-18,22-27';
my $replace = 'B';
my $in = join '-', 1 .. 30;
my $want = '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';

my %X = map { $_ => 'X' } map { /-/ and $` .. $' } split /,/, $ranges;
my $out = $in =~ s!\d+! $X{$&} // $& !ger =~
  s/[-0-9]{2,}/ $replace ^= 'A'^'B'; $& =~ s|\d+|$replace|gr /ger;

print "ranges $ranges\n   out $out\n  want $want\n";
$out eq $want or die "**Mismatch**";