Has to be sed. The scripts we had to write as part of UNIX classes... Like:

sed -n '/^[01]\+$/ {:s /^$/ {x; s/^/1/; b n}
s/0$/1/; t e; s/1$//; x; s/$/0/; x; t s
:e G; s/\n//; :n p; x; s/.*//; x; d}'

This one adds one to a given binary number :-)