Changing the current tag value

Changing the current tag value, $T
The  control sequence is used to change the current rewrite rule tag. The rewrite rule tag is prepended to all rewrite rule patterns before they are looked up in the  configuration file/  group  and domain database. Text following the , up until either an at sign, percent sign,   ,  ,  ,   ,  , or  , is taken to be the new tag.

Tags are useful in handling special addressing forms where the entire nature of an address is changed when a certain component is  encountered. For example, suppose that the special host name , when found in a source route, should be removed  from the address and the resulting address forcibly matched against the  channel whose. This could be implemented with rules like the following (  is assumed to be the official name of  the local host): internet             $S$U@localhost$Ttcp-force&#x7c; tcp-force&#x7c;. $U%$H@TCP-DAEMON The first rule will match the special host name   if it appears in the source route. It forcibly matches   against the local channel, which insures that it  will be removed from the address. A rewrite tag is then set. Rewriting proceeds, but no regular rule will match because of the tag. Finally, the default rule is tried with the tag, and the second rule of this set  fires, forcibly matching the address against the channel with   of ,  regardless of any other criteria.

See also:
 * Rewrite rule template substitutions and control sequences