my @channels = (1, 1, 0, 1, 1, 1, 0);
my @vals = map { $_ + 1 } grep { $channels[$_] } 0 .. $#channels;

my $val = num2range( @vals );

print $val, $/;

sub num2range {
  local $_ = join ',' => sort { $a <=> $b } @_;
  s/(?<!\d)(\d+)(?:,((??{$++1})))+(?!\d)/$1-$+/g;
  return $_;
}