If you want search for every string that starts with “x”, “ht” or “u” and ends with “ml”, you can write a regular expression like this:
(x|ht|u)ml. Insert this expression in the search editor, click , and enable regular expressions by toggling the button. Please note that using regular expressions lets you to make very complicated searches, but the cost could be a performance degradation. Regular expression can be very tricky, and it is often the case that “if you want to solve a problem with a regular expression, you have two problems”.