use Modern::Perl;
use Number::Rangify qw/rangify/;

while (<DATA>) {
    my $seq;
    my @ranges =
      map { sprintf "%s-%s", $_->Size }
      rangify( grep $_, map { $seq++; $_ eq '-' ? $seq : '' } split // );
    say "@ranges";
}

__DATA__
A---B
A--B---C
ABC--DE
A-B--C----DEF------H