perl -e'$d=shift;$c=sprintf"%0${d}d",int rand 10**$d;@n=split//,$c;x();for(0..$#n-1){$m.=$n[$_];$d--;x();}print$c,$/;sub x{for(1..1e5){printf"$m%0${d}d\n",int rand 10**$d}}' 10