Randomization.

• $random : return an 32-bit signed random number.
• $urandom : return an 32-bit unsigned random number.
• $srandom(seed) : set random seed for $urandm.
• use run-time switch : +ntb_random_seed=seed_value
• $urandom_range(min, max)
• randcase

randcase
   10 : f1();
   20 : f2();
   30 : x = 100;
   50 : randcase ... endcase; // nested
endcase