When the last number is known, the first number has the same remainder as the last number when divided by 4. The second number is one of the possible first numbers plus 2 (wrapping to 0 at 40). The range of numbers is 0 to 39.

Example output if the last number is 19:

3-5-19
3-9-19
3-13-19
...
39-33-19
39-37-19
39-1-19
[download]

My current attempt is posted below. Enjoy :)

(I suspect further restrictions can be made to the key space to reduce the number of possible combinations (ie first and last number can't be the same) but this initial iteration does not consider these.)

[1] With reference to:
http://www.dontforward.com/masterlock.htm
http://www.fusor.us/lockpick.html

master_lock_combo(19);

sub master_lock_combo
{
#0        1         2         3         4         5
#12345678901234567890123456789012345678901234567890

@x=grep{$_[0]%4==$_%4}0..39;for $i(@x){for
(map{($_+2)%40}@x){print"$i-$_-$_[0]\n"}}
}
[download]