If you use $1, regex would capture the whole word. You may notice that there is an extra pair of parentheses in the pattern.

You can remove that outer pair, so you can use $1 and $2 instead.

Why use $3 and $2 instead of $1 and $2?
Very nice solution though

Nice solution

How does this work? I know this is essentially n >> 1 but I thought right shifting by 1 would divide by 2 instead of multiplying by 2?

the chars are submarine?