Select Code to Download

  (caller)[3] eq 'fib' or ($nth !~ m{^\d+\z}a or @_) and die $fib_die_
+msg;

use strict; use warnings;
use 5.20.0;
...
}

say fib @ARGV;

sub fib :prototype($) ($nth : Uint) {
  # check for 1 == @_ already done
  ...
}