given($_) {
      when (/^abc/) { $abc = 1; }
      when (/^def/) { $def = 1; }
      when (/^xyz/) { $xyz = 1; }
      default { $nothing = 1; }
   }
# and similarly
   given($foo) {
      when (undef) {
         say '$foo is undefined';
      }
      when ("foo") {
         say '$foo is the string "foo"';
      }
      when ([1,3,5,7,9]) {
         say '$foo is an odd digit';
         continue; # Fall through
      }
      when ($_ < 100) {
         say '$foo is numerically less than 100';
      }
      when (\&complicated_check) {
         say 'a complicated check for $foo is true';
      }
      default {
         die q(I don't know what to do with $foo);
      }
   }