sendmail, 4th Edition

It is often valuable to group rule sets by function and call them as subroutines from a rule. To illustrate , consider the following rule:

R $+ < @ $+ > $: $> set

Here, the RHS $> set operator tells sendmail to perform additional rewriting using a secondary set of rules called set . The workspace is passed as is to that secondary rule set, and the result of the rewriting by that secondary rule set becomes the new workspace.

The $> operator is described in full in Section 18.7.4.