You could avoid those ugly ifs before every printout by saying

if ($opt_c) {
    $\ = "\n";
} else {
    $\ = " ";
}
[download]

at the top of your program (see perlvar). Your prints then simply become print; or print $y;

And two random remarks, you might be interested in this recent thread, also dealing with the Fibonacci series and I hope you developed your program using strict and warnings :)

-- Hofmator