perl -e "$h{6}=$h{7}=1;for (@ARGV){print qq($_ ) unless exists $h{$_}}" 1 6 2 2 7 1 6 99 99 7

In this case, exists is not needed, because all numbers in the blacklist have values that evaluate to true:

>perl -e "$h{6}=$h{7}=1;for (@ARGV){print qq($_ ) unless $h{$_}}" 1 6 
+2 2 7 1 6 99 99 7
1 2 2 1 99 99
>
[download]

And for the same reason, we can shorten that a little bit more by using OR instead of postfix unless:

>perl -e "$h{6}=$h{7}=1;for(@ARGV){$h{$_}||print qq($_ )}" 1 6 2 2 7 1
+ 6 99 99 7
1 2 2 1 99 99
>
[download]

Switching to postfix for gets rid of a few more characters:

>perl -e "$h{6}=$h{7}=1;$h{$_}||print qq($_ )for@ARGV" 1 6 2 2 7 1 6 9
+9 99 7
1 2 2 1 99 99
>
[download]

Alexander