Alternative |

Alternative matches one of the specified patterns, which are separated by |.

(http|ftp)://	http:// or ftp://
table|tr|td	table, tr, or td
(https?|ftp)://	http://, https://, or ftp://

You often have to use parentheses for grouping, as is shown in the first example. Without parentheses, this example will be interpreted as “http or ftp://”.