@start = (1,2,8,9,10,11,12,43,66,109,121,122,123,657);
@queue = ();
@output = ();

print 'start :: ' , join(',',@start) , "\n";

foreach (@start) {
	if( ($_ - $queue[-1]) == 1 ) {
		# part of sequence
		push @queue, $_;
	} else {
		# store sequence
		push @output , (@queue > 2) ? $queue[0] . '-' . $queue[-1] : @queue;
		@queue = ($_);
	}
}

push @output , (@queue > 3) ? $queue[0] . '-' . $queue[-1] : join( ',' , @queue );
print 'Expected :: 1,2,8-12,43,66,109,121-123,657' , "\n";	
print 'End :: ' , join(',', @output);