Another way:

c:\@Work\Perl\monks>perl -wMstrict -le
"my $x      = 0b10001010;
 my $target = 0b10001101;
 ;;
 my $mask = $x ^ $target;
 ;;
 my $result = $x ^ $mask;
 printf qq{0b%b \n}, $result;
 ;;
 die qq{target $target != result $result} if $target != $result;
"
0b10001101
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