Your first code seems to want to remove a certain char specified by it's numeric representation, and its preceeding char. $backsp(this is a test,$asc(i)) returns tss a test. You don't need a while loop for that, you can use the /g modifier that will make the regex engine repeat the pattern on the string until all matches have been made.
You do need a while loop, as several backspace characters can be next to eachother..
