Your code works fine, but it includes 250 and excludes 500.

Direct quote from perldoc -f rand:

               Apply "int()" to the value returned by "rand()" if you 
+want
               random integers instead of random fractional numbers.  
+For
               example,
 
                   int(rand(10))
 
               returns a random integer between 0 and 9, inclusive.
[download]

With this in mind take a look at my reply and apply a small tweak:

my @answers=();
push @answers,(int(rand(251))+250) foreach (0..99);
[download]

The sequence int(rand(251)) will now produce integers in the range of 0..250 and when added to 250 will produce 250..500.