Concatenate two primes is also prime

Concatenate two primes is also prime is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

Task

Concatenate two primes (p1,p2) is also prime, where p1,p2 < 100

Ring

<lang ring> load "stdlib.ring" see "working..." + nl see "Concatenate two primes is also prime:" + nl row = 0 prime = []

for n = 1 to 100

   for m = 1 to 100
       ps1 = string(n)
       ps2 = string(m)
       ps12 = ps1 + ps2
       ps21 = ps2 + ps1
       p1 = number(ps12)
       p2 = number(ps21)
       if isprime(n) and isprime(m)
       if isprime(p1)
          pf = find(prime,p1)
          if pf < 1
             add(prime,p1)
          ok
       ok
       if isprime(p2)
          pf = find(prime,p2)
          if pf < 1
             add(prime,p2)
          ok
       ok
       ok
   next

next

prime = sort(prime) for n = 1 to len(prime)

   row++
   see "" + prime[n] + " "
   if row%10 = 0
      see nl
   ok

next

see nl + "Found " + row + " prime numbers" + nl see "done..." + nl </lang>

Output:

working...
Concatenate two primes is also prime:
23 37 53 73 113 137 173 193 197 211 
223 229 233 241 271 283 293 311 313 317 
331 337 347 353 359 367 373 379 383 389 
397 433 523 541 547 571 593 613 617 673 
677 719 733 743 761 773 797 977 1117 1123 
1129 1153 1171 1319 1361 1367 1373 1723 1741 1747 
1753 1759 1783 1789 1913 1931 1973 1979 1997 2311 
2341 2347 2371 2383 2389 2917 2953 2971 3119 3137 
3167 3719 3761 3767 3779 3797 4111 4129 4153 4159 
4337 4373 4397 4723 4729 4759 4783 4789 5323 5347 
5923 5953 6113 6131 6143 6173 6197 6719 6737 6761 
6779 7129 7159 7331 7919 7937 8311 8317 8329 8353 
8389 8923 8929 8941 8971 9719 9743 9767 
Found 128 prime numbers
done...