This configuration variable determines whether setting the XFD_MAP adds to or replaces the existing value. When this variable is set to "0" (off, false, no), setting the XFD_MAP adds new value patterns to the end of the existing value. When it is set to "1" (on, true, yes), setting the XFD_MAP replaces the existing value with a new value. The default value is "1" (on, true, yes). This variable may be useful if you need to include multiple XFD_MAP lines in a configuration file, and want to avoid setting and resetting the variable. When multiple lines exist, all patterns are used in the order they are listed.