I quite like your use of the ternary operator there. I tend to be reluctant to use it because of the usual increased readability of explicit if/else statements (at least in most of the code that I write), though in this case I think it is well suited to the task.

I think there's a limit to the value of explicit step-by-step variable assignment and use, however, for readability. In this case, the arithmetic formula used to produce results seems obfuscated by being broken up the way you've done so -- though it may well just be a matter of taste, or I may just be weird to think it's more readable to keep the formula a little more integrated.

I'd appreciate it if you'd have a look at the relevant parts of my response to liverpole, and perhaps comment on the way I used explicit variable names for the start and end integers, adjusting perhaps for the use of the ternary operator.

In fact, I'll cut out the middleman and provide a version of the relevant snippet using the ternary operator:

my $start = ( $opt_s ) ? $ARGV[0] : $ARGV[0] + 1;
my $end = $ARGV[1];

print( ($end - $start + 1) * ($start + $end) / 2 );
[download]

edit: code typo pointed out by kyle at roughly the same instant I noticed it myself