Name
$#
Synopsis
Because the RHS can return a delivery-agent specification, it is
sometimes desirable to check for the $#
operator
on the LHS of a rule. Consider, for example, the following rule:
R $+ $| $# OK $@ $1
The LHS looks for anything (the $+
) followed by a
$|
operator, and then a $# OK
.
This might match a workspace that was set up by a database-map lookup
or a call to another rule set. The $# OK
means the
address was OK as is, and so should be placed back into the
workspace. The RHS does just that by returning (the
$@
prefix) the original address (the
$1
references the LHS $+
, which
contained the original address).
Note that the $#
operator has no special meaning
in the LHS. It is used only to detect a delivery-agent-like
specification made by an earlier rule on the RHS. The next two
sections reveal how this is done.
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