USE warnings;
USE strict;
 
MY $length = 7; # the amount of numbers per string
MY $max = 1000; # the number of strings
MY @strings; # array to store the strings
FOR (1..$max) {
   PUSH @strings, rand_nums($length);
}
PRINT "$_\n" FOR @strings;
 
{
   MY %cache; # create a "static" variable
   SUB rand_nums {
      MY %local_cache; # create a new hash
      MY ($length) = @_; # the length of the random number string passed to the sub
      MY $serial = INT(RAND(49))+1; # get the first number for the serialized string
      $local_cache{$serial} = 1; # store the first number in the hash
      FOR (2..$length) {# start at 2 because we already have the first number
         MY $num = INT(RAND(49))+1; # get a new random number
         REDO IF EXISTS $local_cache{$num}; # redo the loop if the number already exists
         $local_cache{$num} = 1; # store the number in the hash
         $serial .= "-$num"; # append to the serialized string
      }
      rand_nums($length) IF EXISTS $cache{$serial}; # redo the function if the key already exists
      $cache{$serial}=1; # store the new key in the hash (%cache)
      RETURN $serial;
   }
}