The Regex Coach - Tutorial step 13

Now select the "Replace" tab, type a new regular expression - (?:x|y+) - into the regex pane, and type the character * (an asterisk) into the first replacement pane (the one with the headline "Replacement string").

Screen Shot

The second pane in the replacement area (the one with "Replacement result" above it) shows the result of replacing the first match with what you've typed into the first pane.