Specific amount of letters/digits

[Snoopy]

well i think the fastest way is to use a maskfile with all possible masks

starting with

Code:

?d?d?l?l?l?l?l?l?l?l?l?l

then shifting the second ?d until you reach the end so from 

Code:

?d?l?d?l?l?l?l?l?l?l?l?l
up to
?d?l?l?l?l?l?l?l?l?l?l?d

then start again with both ?d?d shifted once 

Code:

?l?d?d?l?l?l?l?l?l?l?l?l

and from there  again shift the second ?d until your reach the end

you should end up with 66 or 65 (11 +10 +9 ... + 1) masks, not quite sure about the last one, representing all possibilities

you can shuffle the resulting lines to achieve add some randomluck or just stay with this order